I would comment that once Peter learned something he did or said was wrong, he stopped doing that. I think that goes for all those ancient saints, sin by sin dropped out of their lives. Peter stopped doubting, Paul stopped persecuting, both plunged full forward into the gospel ministry. We all start off weak concerning sin and even knowing what it is, but the danger we greatest danger we faced was for those knowing to leave us in our sin such that we are left self deceiving. Each one of us came to learn what was wrong through teachings of rules and eventually laws and regulations. Even the Gentiles practiced enough law among themselves to exhibit a measure of God's law in their hearts. They stood to be judged according to their own laws, which we know would be a dangerous route to take. But the sons and daughters of the Gentiles had no alternative, caught up in those world ways.
I spent years smoking cigarettes, even after learning about the health risks. I dreaded the possibilities, like a sinner dreading hell. But I chose to keep smoking until diagnosed with a spot on my lung. When I rushed in for prayer, a preacher told me to let God help by no longer play-acting like the Marlboro Man in the TV ads, I being given away about that by the yellow stain above my lip. I repented and quit cold turkey by the power of the Lord conquering yet another sin habit of damaging my health and witness.
It appears to me the Devil never gives up on keeping the ignorant ones, the lost, especially those who have been exposed to a little truth of the reality of the living God, of Jesus, and a glimmer of righteousness. If I were Satan, why not do all possible to keep someone from gaining enough revelation to become a new creature in Christ? It's a lot more difficult to ruin a true disciple of Christ who has tasted the benefits of obeying the new Master Jesus! That person is on guard, unlike someone with just enough religion to make their knowledge toxic to themselves and others.
Sin by sin, the Lord will take us to task, expecting a change of direction He provides. But that requires listening, seeking, knocking, making up the mind to change by that power not of ourselves, but of the Holy Spirit within.
The issue of "nature" for man to sin by is misunderstood often. People are not born to be like a wild hog that for all its life would, if taken in as a pet, would devour its master once found asleep. The Gentiles having laws to themselves proves there is a distinct creation of human beings in the image and likeness of God, else none of us could ever rise above hopelessness.
The Law served one purpose, to train people up as to what sin is, and that sin has consequences. It causes an inward battle, a struggle of conscience concerning the righteousness of God. The Law saves none. Jesus saves.