Peter’s letter was written in a time where the prevalent Roman culture of the day had growing obesity problems with excessive consumption, orgies, and self-indulgence seen as human rights to be enjoyed. The Western world today certainly has the same ideals—people struggling to control their desires and having no shame in eating or drinking to excess. As Christians we are to control our appetites, our tongue, and our thirst for wealth and possessions. We must not be mastered by these things.
Peter assumes that self-control is a virtue that must be pursued because it is a virtue with which we struggle. He is thus being very realistic in this list, recognizing that Christians continue to sin and need to fight against the sinful desires that remain.
One area where many people struggle with self-control is relationships. It often happens that someone really enjoys spending time with a certain boy or girl and even though they might know he/she is not a Christian, they find a way of justifying the relationship. If marriage ensues, they eventually realize their partner is not keen on the Christian faith and is trying to stop them from attending church. Because they did not make every effort with self-control, they end up being in a position where it is really difficult to follow Christ. A lack of self-control is thus a doorway to falling away from faith in Christ.
6 and knowledge with self-control, and self-control with steadfastness, and steadfastness with godliness,