What in your past do you hope never sees the light of day again? You have three options for making peace with it, but only one will work.
One: You can ignore it and hope it never resurfaces. How did that work out for King David? Do you really want to carry the burden of your guilt for the rest of your life?
Two: You can punish yourself. Guilt is the price good people pay for bad deeds. If God won't discipline us, we'll punish ourselves. We continue to beat ourselves up over mistakes made and failures committed until we feel that we have paid our debt.
Three: You can believe in grace. All sin is ultimately against God: "Against you, you only, have I sinned and done what is evil in your sight" (Psalm 51:4). So only God can remove it. If we confess our sins to him, "he is faithful and just to forgive us our sins and to cleanse us from all unrighteousness" (1 John 1:9). He then removes our sin from us "as far as the east is from the west" (Psalm 103:12), casting it "into the depths of the sea" (Micah 7:19) and remembering it no more (Isaiah 43:25).
So confess those parts of your past that burden you today, specifically and with a repentant heart. Claim the fact that God has forgiven and forgotten all you confessed to him. The next time guilt strikes you, say to it: "I confessed that to God, and grace is greater than guilt." You may have to say it 100 times today and 90 times tomorrow, but eventually the grace will defeat the guilt in your soul and you'll be free.
Shrek was a sheep in New Zealand. He lived by himself for six years, then was caught on April 15, 2004. His fleece had grown to weigh 60 pounds. His shearing was broadcast on national television; it contained enough wool to make suits for 20 men.
Jesus is our "good shepherd" (John 10:11). If we come to him, he will help us "lay aside every weight, and sin which clings so closely" so we can "run with endurance the race that is set before us" (Hebrews 12:1). Your culture sees what you've been; God sees what you can be.