The Spiritual Declension of the Soul (Video) — Michael Durham

A Prayer for God’s Presence and Revival

This is the cry of our hearts that we need you. We need you more than we realize. And we are amazed at your majesty and greatness this morning. For you to come to us, you must humble yourself because you're so vast and infinite and beyond us.

And when we come to you, we must humble ourselves because we're so proud and arrogant and self-sufficient that we would cry out, Oh, who are you that you would be mindful of us? Visit us now through thy word.

Thy word is truth. Let the spirit, the wind of the spirit blow. Breathe on me, O Lord. Let me be thy rod and thy hand. Do your perfect will. I pray for this, my hearers, that they, too, would receive the gust of the spirit, that they would know your nearness, that they would know that they are in the presence of Almighty God, that you would come and make this ground sacred because of the manifestation of your glory.

Oh, God, visit us here in this hour. Transform it, Lord. Change it from just the routine Sunday morning and sanctify it with something divine, heavenly, holy. Oh, Lord, we call upon you now. For if you will not work, our labor is in vain.

What I do, Lord, will have no merit, no work, no power, no lasting quality about it. But our hope is in you. As we've just heard, you will not break a bruised reed or you snuff out the moldering, smoldering flax.

You're kind, you're good, you're compassionate. You care more about us than we care for ourselves. You love us with a love that's boundless, immeasurable, immense. Surely, Lord, you see our need of you this hour and our need pulls your heart closer towards us.

Oh, even now, Lord, let those billows of love from your heart flow into our heart. Holy Spirit, come for the glory of the one who sits at your right hand, Father. For his sake, come and magnify him, I pray.

In Jesus' name, amen. The text I pray the Lord be pleased to speak to us from is Paul's epistle. If you're reading from the King James Version, Paul's epistle to the Hebrews, chapter five, verses eight through 14.

The epistle to the Hebrews, chapter five, verses eight through 14. I want to speak on the theme this morning, spiritual declension. Spiritual declension. Hebrews, chapter five, beginning with verse eight.

I'll be reading from the New King James Version this morning. Though he was a son, yet he learned obedience by the things which he suffered. And having been perfected, he became the author of eternal salvation to all who obey him.

Called by God as high priest, according to the order of Melchizedek, of whom we have much to say and hard to explain since you have become dull of hearing. For though by this time you ought to be teachers, you need someone to teach you again the first principles of the oracles of God and you've come to need milk and not solid food.

For everyone who partakes only of milk is unskilled in the word of righteousness for he is a babe. But solid food belongs to those who are of full age. That is, those who by reason of use have their senses exercised to discern both good and evil.

Spiritual Declension Is Possible for Christians and Churches

Verses eight through ten of our text is a continuation of a discussion on the priesthood of Jesus Christ. It begins in the fourth chapter, verse 14. And so, verses eight, nine, and ten of this, our text, is only the continuation of that same discussion.

He's teaching that Jesus is our high priest and that he's not after the order of Aaron, but after the order of Melchizedek. And then in our text, verse 11, he abruptly changes, he turns on a dime and says, I want to explain further about this great priesthood of our high priest, but I can't right now.

It's hard to explain, not necessarily because it's such deep spiritual truth, but because you've become dull of hearing. The problem is not the doctrine, the problem is the hearer. You've become dull of hearing.

I wish I didn't have to take necessary time to answer the question, but I feel like I must. Is spiritual declension possible for a Christian or for a local church? The reason the question needs to be addressed is because there are some today who believe and teach that revival is not necessary among the people of God.

Spiritual declension is not a possibility, and they say this for this reason. God has made a covenant with you. He's made a covenant with his people, and that covenant states that he would rid us of all of our idols, he would cleanse us of all of our filthiness, that he would so work in our hearts to cause us to walk in his statutes and to do his judgments.

He is a wonderful, kind bridegroom who nurtures his bride. He washes her with the water of the word. Therefore, know she is in a perpetual state of sanctification. And besides that, backsliding, that old Baptist term, is not a New Testament word at all.

It's an old covenant term dealing with a people, unregenerate for the most part, who kept backsliding, sliding backwards into idolatry and away from God. And then he would send a righteous leader, and they would be a revival back to the one true God.

And once again, they would slide backwards into idolatry. You don't even find the word backsliding in the New Testament. Is this correct? And I say to you, our text argues strenuously, no. Spiritual declension is possible.

In fact, I feel rather safe in saying some of you are in its grips even right now. In Psalm 119, verse 67, the psalmist says, Before I was afflicted, I went astray. But now I keep your word. In other words, there was a time he was walking obedient, and then there was a period in time in which he was walking in disobedience.

But because of the discipline, the loving hand of God in his life, now he's been brought back. There's been revival. He's been restored to obedience. Ah, but you see, you say, that's an Old Testament text.

Well, my dear friends, the New Testament, while the word backsliding may not be found, its principle is all through the pages and chapters of our New Testament. For example, in Revelation chapter 2, Jesus, listen to what he says to that wonderful, solid, orthodox, and may I be so bold to say, reformed church, Ephesus.

Nevertheless, I have this against you, that you have left your first love. Now, this is not an average church. This is a cut above the average. This is an early church, a New Testament church, who had, if I can say this reverently, some celebrity pastors.

The apostle Paul planted, started the church, and was its first pastor. In fact, he stayed longer in Ephesus than he did any other place where he planted a church, three years. And then his successors aren't too shabby either.

Timothy followed him there and pastored that church. And last but not least of all, the immeasurable, the wonderful, the beloved, the apostle John was a pastor at the church of Ephesus for years, well acquainted with these people.

And now he taps this St. John on the Isle of Patmos, exiled for his labors in the ministry, and says, I want you to tell them, they've done wonderful things in their doctrine, their labors I am commending, but they have missed it in the most primary area, their love for me.

They've declined. They've gone backwards. They don't love me like they used to love me. And I don't know about you, but I cannot read James 4 without hearing the necessity for revival. James 4, verse 4, listen to this salutation, to a local church or churches, adulterers and adulteresses, do you not know that friendship with the world is enmity with God?

Whoever therefore wants to be a friend of the world makes himself an enemy of God. That's not applicable to the sinner. If you're not a Christian here, my friend, I want you to understand, you have not become an enemy of God.

You are and always have been. You're against Him, not for Him. But here the context is clear. He's writing to Christians who have chosen to become more friendly with the world and automatically that makes them an enemy to God.

What's the answer? Verse 7, Therefore submit to God, resist the devil, and he will flee from you. That's not the counsel to the sinner, no. That's the counsel to a Christian who's in spiritual declension.

Draw near to God and He will draw near to you. Cleanse your hands, you sinners, and purify your hearts, you double-minded. Lament and mourn and weep. Let your laughter be turned to mourning and your joy to gloom.

Listen to this. Humble yourselves in the sight of the Lord and He will lift you up. That's the promise to God's people. Humble yourself and I will lift you up. So yes, spiritual declension is not only in the New Testament.

It's alive and well today and it's possible that some of you are in that state. And the answer is a revival. Now this word revival has come because of use and abuse upon hard times. When we use the word, we normally think of this great outpouring of the Holy Spirit, this extraordinary work where if hundreds if not thousands are brought into the kingdom in a short duration of time and certainly that is an amazing work of God.

Revival as a Return to Normal New Testament Christianity

But the truth be known, the word revival doesn't have much to do with the lost man, the unregenerate person because they don't need revival. They need another R word, resurrection. You can't revive something that hasn't been alive.

Revival is for the Christian. It's for the individual or a local church. A revival, what does it mean? Well, here's how I define it. Revival is simply a return to normal New Testament Christianity. That's all it is, all it's ever been.

A return to normal New Testament Christianity. What does that look like? Walking in the Spirit continuously, consciously aware of the presence of God. That's all that means. That's normal New Testament Christianity.

And anything less than that is subnormal, abnormal. Is it possible we have become so accustomed to the abnormal that it's become the norm? I say as I travel around preaching, I often repeat this statement wherever I go, you can have as much of Jesus as you want and you will always have as much of Jesus as you want.

How much do you want of Him this morning? Are you content to remember better days in your relationship with Christ? Has a lethargy seized your heart? Has there been for you what was true of the church at Ephesus?

A departure, a departure from love that was fervent, full of vigor and vim. Can you remember those days? And are they only a memory and not a vital reality today? Oh, spiritual declension is very possible.

And there are common mistakes that I think that we as God's children make that leads to this spiritual neglect of our own souls. There are many. I don't have time to give you all that I could this morning, but let me give you three.

A Low View of Sin and Spiritual Declension

The first is a low view of sin, particularly the sin of spiritual declension, spiritual decline, going backwards rather than progressing in your relationship with God. The first thing you must know and believe about spiritual declension is that it's the betrayal of the Christ who lives within you.

It's no less severe than the denial of Peter and the betrayal of Judas. It is of the same essence, my friend. Now, Judas, he was not regenerated, but Peter was, and therefore his treachery was all the more reprehensible.

Peter's denial began long before a servant girl confronted him and accused him of being a follower of Jesus. No, that was the culmination of his spiritual decline. Even Jesus, our Lord, witnessed and saw it before it happened and warned Peter.

It is this spiritual declension, this process of decay that we don't think rightly about. We believe all is well so long as sin is not manifested. As long as there's no violent or flagrant transgression of commands or prohibitions or scripture, things are okay.

Maybe my relationship has been better. My devotional life may have been more fervent, but I'm not in disobedience. I'm therefore walking with God. But in the eyes of him with whom we have to do, the seed is no less poison than the fruit.

The seed is as venomous as the sin which it produces because it is sin. It is. No matter the degree or the demonstration of your declension, it is sin. And oh yes, at first, the decline may not seem to be difficult or hard, but it's the same spirit that influenced Peter to swear he knew not the Lord.

Spiritual declension is of the same essence as the sin it produces because it is sin. It's not a small matter. Spiritual declension, even in its initial and embryonic form, is the spirit of betrayal, the betrayal of the one that loves you most.

And because we don't see the problem as being an act of betrayal, we tolerate the causes, the causes of spiritual decay. We tolerate them. We even nurse them. We quickly dispel any notion that the beginning of rot is the same disease that brings destruction, like a cavity in the tooth.

As long as you ignore it, it will eventually destroy the tooth. Not too long ago, I met a man who had just left the doctor having a tooth extracted. And I said to him, what happened? He said, well, I had a cavity.

Well, of course, then I asked the natural, obvious question, well, why didn't you go to the doctor and have it taken care of long before now? He said, that was the funny thing about all of this. I didn't even know I had a cavity.

And then I began to feel a pain. I immediately went to the dentist and he said, I'm sorry, but it's too late to save the tooth. The rot is too pervasive. And that's just what spiritual declension is like.

We pay it no mind. We think it no great matter until it's too late and we have shamefully sinned and brought reproach upon our dear Lord. Let me ask you some very tough questions. But don't avoid them.

Apply them. Do you not realize that even if you haven't yet publicly brought discredit upon Christ, that by your lack of spiritual zeal, Christ already feels wounded? Do you think He doesn't feel your departure from first love?

Are you sure that your little affection does not hurt His heart? Are you so sure that you would continue to be negligent in the care of your soul and so I say a low view of this heinous spiritual problem is a severe mistake and it has no good outcome, dear friend.

It has no good outcome. You've got to see and believe that any, any heart departure or decline is grievous to the Lord Jesus. It is sin. It is sin because it violates the greatest commandment to love the Lord thy God with all thy heart, with all thy soul, with all thy mind and all thy strength.

There is no way to excuse it in light of that word. A second common mistake we make. We either do not know or we have forgotten that God's activity of grace must be cooperated with. God's activity of grace in you must be cooperated with.

Cooperating with God’s Grace in Sanctification

God's grace in your sanctification does not do all you need it to do but it supplies all you need. Doesn't do all you need but it supplies all you need. God's grace does not rule out our cooperation. It enables cooperation.

I travel a lot as you know and I'm talking about good orthodox sound churches. Most Christian in churches today are either in one ditch or the other when it comes to the role of God and the role of man in the Christian life.

The majority are confused. God does command me to repent. Yes, God commands me to obey Him and yes, God commands me to trust in Him but God's not going to do my repenting, obeying or trusting. He does give me the desire and the power to do all of the above and the power is in my spirit and it lies within my will but dear friend, I must exert that will.

I must exert myself. I'm the one that has to buffet my body. I'm the one that must put on Christ and make no provision for the flesh. God requires cooperation but grace also supplies both the desire and the power to cooperate with it and yet many professing Christians are just simply lazy.

They've been made lazy by a misunderstanding of the preserving quality of grace or they're just by temperament lazy but either way, they're lazy. We want God to do everything for us. Some believe grace energizes us like a battery and so they just passively watch God do His thing through them and I no doubt there's someone here like that this morning.

You're waiting for the thunder and the lightning called grace to hit you today and thereby change you and make you in a super saint. You're praying, begging. Oh God, do something. Give me this kind of experience that somehow solves my disobedience problem forever.

It doesn't work that way, friend. Or you passively just simply do your own thing thinking that grace is some kind of liberty where you do the best you can and excuse the rest. That's how some people define grace these days.

They view the Christian as nothing more than a forgiven sinner and grace manages his sin problem by merely canceling out the penalty. They do not believe grace has anything to do with growing in holiness.

I've had people confront me, insult me, hackle me even while preaching when I introduce the subject of holiness without which no man shall see the Lord. They say we're saved by works, excuse me, by grace and works has nothing to do with it.

Yes, but where in this book does the Bible say that grace is against works? It says it's against the idea of earning but it's never against the idea of effort. It enables effort. I believe all unbiblical views concerning grace is a problem and here it is namely separating the grace of God from God.

Here's where the problem stems. Here's the root. God's grace is not a commodity dropped into a person's heart. It's not some impersonal force like the force in the Star War movies. Absolutely not. Grace is nothing like that nor is it just God's undeserved love toward us.

No, instead grace is God's undeserved love toward us that motivates Him to intervene in our lives. The grace of God and all of the graces of God are God's activities within you. It's God Himself acting on your behalf.

For example, when we speak of the grace of regeneration we don't mean some abstract impersonal force that changes the heart of the sinner. Absolutely not. We say that's God Himself active working within the human soul.

It's God doing it. It's a demonstration of His undeserved love for you. It's He giving Himself to you in this wild and extravagant and incomprehensible love. It's God Himself working in you. That's what grace is.

It's God work. And therefore because God is a person, we must engage Him. We must interact with Him and His activity as the work of a person. This engagement is the very means of relationship. It's what we would mean by the words practicing relationship.

Our relationship with Christ, now listen carefully, is not self-sustaining. It's not perpetual without our engagement. In other words, no relationship works when only one party is working. And grace given to you, the activity of God, means you must engage yourself not with some inadimate impersonal force, but with the reality of Jesus Christ.

How real is Jesus to you, friend? This is what we're talking about. The reality of Christ lived out daily. Are you engaged with Him? Are you cooperating with Him? And since God's grace is His activity, then we've got to learn how to interact with God.

And the more you interact with this Christ who dwells within you, the more of His grace you are experiencing. Does that make sense? Does this make sense? You can pray and ask God for grace, but what you're really asking is God to get involved in your life and you to get involved in Him.

That's what you're really asking for. And I pray you're asking for that. I pray you're asking for that. The final common mistake I want to deal with is that we wrongly assume that the Christian soul is not hostile to grace.

The Soul’s Hostility to Grace and the Hidden Roots of Decline

We assume now that we're a Christian. My soul is a wonderful environment for God's activity and His work. But the truth really is, according to the Scriptures, your unperfected soul is not a friendly environment for His activities or His work.

Not only are the assaults on grace from without, they are also coming from within the soul. We either do not know or we have forgotten that every Christian has within him or her the makings of the worst possible backsliding.

The devil's not required for a spiritual fall from fellowship with God. The seeds, listen, the seeds of such a fall have all they need within you already without the cultivation of Satan. Listen to what James 1, verse 14 says, but every man is tempted and drawn away by his own lust.

There's enough corruption in me to deter me and swerve me from him and I don't even need Satan's help. I can do it all by myself. Your soul is not the best place for grace, but thank God He is gracious to remain nonetheless.

Now the most significant problem with backsliding, spiritual declension, decline, whatever you want to call it, is that in its earliest forms or its initial stage, it's really hard to detect. It's very difficult to recognize.

Most Christians have not learned how to detect the very early stages of spiritual declension and that's why we find ourselves in it. It's tough to detect. In fact, because of your human makeup, your inherent pride, a man or woman can go far into spiritual declension before they even realize it.

And when do they normally realize it? When a sin happens. Just recall Samson. Samson, who had the Holy Spirit's power on him while he was consorting with the enemies of Israel. Listen to what Delilah says to the compromised champion.

The Philistines are upon you, Samson. And the Bible says he awoke out of his sleep and said, I will go out as other times before and shake myself. And then comes those sad, sad words. And he knew not that the Lord was departed from him.

He knew it not. Stealth of declension is so destructive that if you don't know how to guard yourself, you will fall prey to it eventually sooner rather than later. You've got to learn how to recognize it.

You've got to learn how to spy it out, discern it, know it, know its tactics. And so therefore, I want to direct your attention to the detection, detection of spiritual declension. How can I recognize it in me before it's too late?

Someone here this morning, you're already within the grip of spiritual decline and you don't even know it. But if you're God's child, I believe this message has been sent to you in order to show you, to help you.

It's His way. It's His grace. It's His means of reaching out to you, calling you. Here I am, come. Draw nigh to God and He will draw nigh to you. One of the reasons that spiritual decay is hard to detect is it doesn't require, now listen, it doesn't require a violation of God's commandments.

You don't have to break a command. You don't have to violate a prohibition of scripture in order to be in spiritual decline. Look at our text. Hebrews chapter 5, these dear Christian had not violated any known commandment.

I would argue, according to chapter 12 and other passages, that they have been doing a wonderful job testifying of the grace and the gospel of the Lord Jesus Christ Because they are a persecuted church.

In the 12th chapter, the writer to the Hebrews says that this persecution is God's loving discipline chasing it in your life. Friends, when the world hates you enough to persecute you, it must recognize something's good in you.

Something of Jesus is about you. There is no known violation. There's nothing like we read about the Laodicean church. Here about these churches in Judea or wherever this letter went. There doesn't seem to be any doctrinal declension.

They don't seem to be less orthodox or accurate in their theology. What's the problem? Verse 12. The problem was they were not growing in maturity. They were not progressing in their sanctification. For though by this time you ought to be teachers, you need someone to teach you again.

The first principles of the oracles of God and you've come to need milk not solid food. Notice the grammar. You've come to need milk and not solid food. Which means what? Grammatically. They had been enjoying a little more solid nourishment but something has happened.

There's been a declension. There's been a decline and now they're back on. Now please, please pay attention. I want to be as practical as I can and helpful as I possibly can by God's help. You don't have to fall into some scandalous temptation to lose your spiritual vigor and strength.

Most of the things we associate with backsliding don't have to happen for a Christian to backslide and that's why it's hard to detect. Another reason it's hard to spy out in the beginning is that all that's required to spiritually decline is to do nothing.

Just do nothing and you will decline. As a young person I used to growing up in the Ozarks of the southern, southwest part of Missouri I used to swim a lot in rivers and there was one famous river we liked to swim in, camp beside the James River and it had a good little current and we would swim upstream and the moment I flipped onto my back to float or tread water, guess what happened to me?

I lost ground automatically. That's what happens when you just simply do nothing. Oh, void prayer. Neglect the prayer meetings. Neglect serious meditation of scripture and your spirit will automatically shrivel.

It can't help it. It's the way it's designed. Be concerned more about good things rather than the primary thing and what is the primary thing? To maintain your fellowship with Christ. That's the main thing.

It doesn't take the place of ministry. Excuse me, ministry doesn't take the place of that. Nothing does. Just do nothing to keep your spirit desperately depending upon the Lord and you will not go forward even though your circumstances seem to progress.

I'm ashamed to tell you but you need to know this. I've experienced many times the blessing of God on my ministry when my heart was not as engaged or engaged at all with God as it had been. Do you hear what I'm saying?

There were times in my ministry preaching, praying, serving the church where I actually saw successes. I saw people saved. I saw answers to prayer. And I knew that my heart was not in full flame for Christ.

Just do nothing to maintain and cultivate fellowship with God and my friend, you're going backwards rapidly and you don't even know it. There's another reason why spiritual declension is hard to detect in the beginning is because your character and your behavior does not change in the beginning of spiritual declension.

Did you hear me? There is no noticeable change in your conduct or your behavior. You still love the things of God. You still love the people of God. You still love Providence Chapel. You love the work of God.

And because you still do, you think everything is proper when everything may not be proper and well. You don't detect any behavioral changes because there are none even though your heart is ailing. You will condemn the sin of others when that same sin's seed is sprouted in your own heart.

It's so invisible, friend. So invisible. That's why this spiritual disease is so damaging and it's why the church languishes. I think it's one of the reasons why we don't see as many people converted as we pray and want to see.

The manifested presence of God is not at work because we are not walking in fellowship with Him in the light as He's in the light. But we think we are. You can function in your ministry gifts while being infected with this malady.

You can continue to pray and read your Bible. Come here. Worship with the saints of God while your heart is languishing, feeling very little, if anything at all. And although the believer is not submitting to the will of God, the life of Christ remains in you.

Now this is the tricky part. God has promised to never leave you nor forsake you. And if God's grace is Him, His activity in your life, it's very possible. In fact, frankly, it does work this way that there are still graces being evident in your life.

There's still evidences of God's activity and work in you. There's glimpses of God's favor. You see now and again the grace of God has not left the child of God and it will never leave the child of God.

But the child can fall from grace. And all of this occurs without your consciousness of it happening. You need to learn how to be aware of it. Because to the untrained heart, the decline is so gradual that it's imperceptible.

It's not noticeable. And you just kind of merrily continue your way until your decline reaches a certain stage and then you can't deny it because now you are violating commandments. You are walking and living in such a way that brings disrepute to the gospel you proclaim.

How many times I've heard people sitting in my office lamenting, crying, I don't know how I got here. I remember one pastor coming to me, wanting to confide in me of great sin in his life and he said with tears streaming down his face, I don't know how I wound up in this situation.

And he was being honest. He didn't realize it because he'd never learned to understand his own heart and to recognize its driftings. The last two or three years, I've known at least three pastors who have fallen and many of them who I have trusted and I've reached out to them and they basically say the same thing.

It's just I don't know how I got to this place but here I am. If we are to detect spiritual declension in its initial form and that's where you want to see it, we've got to rightly define it. So what do I mean by spiritual declension?

Defining Spiritual Declension as a Loss of Fascination with Christ

What is our definition? Well here it is. This is the best way I know how to define it. It's helped me when the Lord showed this to me. Spiritual decline is defined as any lessening, any lessening of the heart's fascination with our Lord.

Now what do I mean by the word fascination? Well that shouldn't be too hard to illustrate. If you're married or about to be married, remember what happened when you met your prospective spouse? What happened to your heart?

Was it not captured? Was it not obsessed with that person? That's fascination. Fascination is to be enamored by something to the point that it almost feels like a spell has been cast over your heart. To be fascinated with Jesus is to be so in love with Him that He is your obsession.

What happens to the mind when it's no longer concentrating on the task at hand? Where does the mind gravitate to? To the obsessions of the heart. The fascinations of the soul. You know what I'm talking about.

Don't sit there like, these are algebraic equations. This is not high math or high science. This is where the rubber meets the road if I can use that terminology. You know your heart's fascinations. You know if Jesus has the obsession of the soul or something else because if it's not Christ it will be something else.

What has your heart? Is it Christ? Do you wake up in the morning with the first thoughts? Him. With the joy and excitement that you're going to be able to spend the first moments of your day alone in communion with this glorious, great, and majestic, and holy, amazing God.

Do you engage Him through the day? Do you walk with Him? Are you fascinated? Just take any curtsy or curricular hobby or something. When you first come on to something like that, man, what do you do? You get on the internet and you research it out.

You study it. You're just thinking. You're obsessed with it. That's fascination. Any lessening of the fascination of your heart towards Christ is spiritual declension. That's it. And so the remedy is that you have to go on self-watch.

Here in verse 14 of our text. He says, but solid food belongs to those who are of full age. That is, those who by reason of use have their senses exercised to discern both good and evil. Your ESV, the Bible probably most of you have open now, says this, but solid food is for the mature, for those who have their powers of discernment trained by constant practice to distinguish good from evil.

Not bad, but not best. Because the word senses is the literal word. I would wish they would have done a more literal rendering. Senses, not powers of discernment. What are your physical senses? And what are they for?

Well, they're the faculties of perception. You perceive stimuli outside and from within the body through the sight, hearing, smell, taste, and touch. It's how we gather in information. The author to the Hebrews is using this word purposely.

He wants you to understand that as there are physical senses, there are spiritual senses as well. You have spiritual faculties by which you can discern good and evil. Not just bad doctrine from good doctrine, but even the fluctuations and the rhythms of your own heart.

He uses another word here. It's the word exercise. Having their senses exercise. This word comes from a word from which we get our English word gymnasium. What's a gymnasium for? It's a place of strenuous activity, discipline, a hard place where you work out, getting in shape, or preparing for some athletic competition.

And then he says, by reason of use. Here I think the ESV does an excellent job in translating. He means being trained by constant practice. Beloved, if you are to understand spiritual declension and know it in your life, you are going to have to constantly practice getting acquainted with the rhythms of your own heart.