Here is why it is so completely important that a preacher actually understands the Bible and conveys it properly.
Your heart is not "wicked," Christian! As a reminder, when the Bible speaks of your "heart," it actually means your mind. The heart organ is only capable of pumping blood throughout your body; everything else we attribute to the "heart" are actually properties of the mind. Yes, Jeremiah 17:9 says, "The heart is deceitful," but that is before Yahweh God's transformation in your life. The genuine Christian believer, upon placing their trust in the person and work of Jesus, has been given a new nature, a new heart, a new spirit, and new desires. Because of this, the believer's heart is righteous and obedient (Ezek. 36:26-27; Rom. 6:17).
Yahweh does not live in dirty places. He cleaned house and moved in. Your heart is not a "fixer-upper"; it is a pristine palace where Jesus resides (Eph. 3:17). Why do you mistrust the very place He chose as His dwelling?
The goal of our instruction is to "love from a pure heart" (1 Tim. 1:5). That is not wishful thinking, it is your reality. Yahweh gave you a heart that is pure—now live from it, whether in marriage, work, or life itself! Living from the heart is not some sentimental fluff. Stop overthinking, over-analyzing, and second-guessing. Trust the new desires Yahweh gave you (2 Pet. 1:3-4).
Sin is not the heart language of the Christian believer. Those rogue thoughts you experience? That is sin operating in you (Rom. 7:17). That is not personal sin, that is the entity of sin that God warned Cain about (Gen. 4:7). You will still be tempted by such thoughts, but you have the power to say "No!" to them (Rom. 6) because you have died to sin. James describes what takes place when we give in to those temptations (James 1:13-15). Your new heart that Yahweh gave you is fluent in righteousness and eager to say "Yes!" to Yahweh.
Christians do not need "behaviour management" as if we are training some wild, savage beast. We have new hearts infused with Yahweh God's Spirit. The goal is not merely to "sin less," but to know Him and live from the heart He gave you! You are not "faking it 'til you make it"; you have already made it. You have been "made complete in Him" (Col. 2:10) and have been "perfected for all time" (Heb. 10:14). Yahweh ripped out your old heart of stone and replaced it with a new heart of flesh that is alive and fully His. The idea that you can "lose" or forfeit your salvation is nonsensical when you actually understand the New Covenant, the Gospel, and Yahweh's grace. When Yahweh spiritually transforms you and changes all these things (regenerating you, making you spiritually alive, giving you a new heart, etc.), unless you are somehow more powerful than God Himself, you cannot change any of that back to its former ways. It would be like a diamond trying to change itself back into a piece of coal.
"The Lord knows those who are His" (2 Tim. 2:19), so Christians need to stop placing themselves as Judge over others (especially those of differing denominations). Yahweh knows people's hearts. We do not. There are people around you who regularly attend service, read the Bible, pray, speak Christianese, etc., who will not make it into the Kingdom of God, and there are those who have seemingly left the faith (Do you know their struggles?) who we will see in the Kingdom of God because Yahweh "began a good work" in them and He is faithful "to bring it to completion" (Phil. 1:6), even if that is on our death bed. Maybe some of these believers encountered issues with the theology they were lead to believe and they mistakenly attributed that aberrant theology to Yahweh, and because they had no good Christians in their lives to help them with such things and get them back on track, the way Scripture tells us to (Gal. 6:1), it appears "they were never saved to begin with." It could very well be true, but we are not God. They may have fled from God, but if He began a work in them, He still has hold of them and will complete that work. Bank on it!
Stop striving and start living—from your new heart, where Jesus lives!