The purpose of Peter’s writing was to encourage the faithful to be holy. Remember the Word of God.
People have mocked the return of Jesus for centuries. They continue on their paths of wickedness and sin, with no fear for God or His judgment. We must not forget that all will occur at the time God has appointed, and it is not for us to know the time it will occur. The Lord is merciful, offering a chance for all to repent. He will come, as He promised. Therefore, we must live Holy lives, in acceptance of His grace, that we may live forever. The patience of the Lord in his return means the salvation of many more souls!
Paul also wrote of these things, and Peter endorses Paul’s letters, putting to rest any possible division. Paul likewise did the same, in his first letter to the Corinthians:
My brothers and sisters, some from Chloe’s household have informed me that there are quarrels among you. What I mean is this: One of you says, “I follow Paul”;another, “I follow Apollos”; another, “I follow Cephas[Peter] ”; still another, “I follow Christ.” Is Christ divided? Was Paul crucified for you? Were you baptized in the name of Paul? (11-13)
As you have been marked by Christ, do not now turn back to your sinful lives, but continue to grow in knowledge and faith. Glory to Jesus.