1. Apologizing and confessing are different.  Confessing is specifically naming the sin to God that you are repenting of, and then making a choice to let it go.
1 John 1: 8If we claim to be without sin, we deceive ourselves and the truth is not in us. 9If we confess our sins, he is faithful and just and will forgive us our sins and purify us from all unrighteousness.

2. Once we confess, we have to forgive ourselves.  God instructs us to forgive men, including us, our sins.  We have to stop bringing up our sin, attempting to punish ourselves.  If we try to do penance for our sins, we are telling God that His Sacrifice which covered all sin, was not enough.
Matthew 6: 15But if you forgive not men their trespasses, neither will your Father forgive your trespasses.

3. We have to stop bringing up our previous sin and allow God to forget our sins.  No matter how ‘bad’ it was, the day you repented (confessed, and let it go), God forgot it.  We have to stop reminding God of what He already cleansed us of.
Isaiah 43: 18Remember you not the former things, neither consider the things of old. 25I, even I, am he that blots out your transgressions for my own sake, and will not remember your sins.