Read: 2 Corinthians 10-13
Marked: 2 Corinthians 12:20-21, For I fear lest, when I come, I shall not find you such as I wish, and [that] I shall be found by you such as you do not wish; lest [there be] contentions, jealousies, outbursts of wrath, selfish ambitions, backbitings, whisperings, conceits, tumults; lest, when I come again, my God will humble me among you, and I shall mourn for many who have sinned before and have not repented of the uncleanness, fornication, and lewdness which they have practiced.
Paul had to address some concerning things in his letters to the Corinthians. His fear was that he would have to severely chastise them and exert his power as an apostle.
So he appeals to them to set their contentions and other disputes aside as Christians should. The things he mentions are unbecoming for children of God, yet, even today churches struggle with these and other issues.
Paul knew that these things can get out of control and lead to more sinful practices. Ultimately, sin must be addressed and an unrepentant heart is a sure sign of an unregenerate heart.
The only sure way to deal with with sin in my life is to confess it and repent resting in the assurance that God will, and does, forgive sin, and do more besides.