A proper doctrine of conversion will give you pastoral power.
Let me jump right in with an illustration. I once confessed a wrongful desire to a friend of mine, and I explained that, frustratingly, my theology knew it was wrong, but part of me was tempted to justify it because it felt “woven into the very fabric of my person” and “part of the very wiring of my soul.” Those were the words I used to explain how much the desire felt like me.
Is it OK for a believer to examine their own life in order to have assurance of salvation? Some say that to do so is an exercise in self-righteousness and pride; they argue that we can and should only look to Christ and his promises for assurance. After all, when we look inside we see nothing but sin and rebellion, what are we going to find in there that will give us assurance?
In a couple weeks I'll be preaching from John 3 where we read of Jesus telling Nicodemus, "I tell you the truth, no one can see the kingdom of God unless he is born again." Before conversion we were spiritually dead. Every inclination of our hearts was warped, perverted. We did bad things because our hearts were corrupt. The world certainly exacerbated our sin, the way a magnifying glass intensifies the rays of the sun--but our hearts generated the sin. It wasn't the fault of bad teachers, bad luck, or bad parents. The problem was in our heart.