But there is hope.
There are three reasons not to feel guilt, but to feel regret:
1. You should not feel guilty because what you have done contributed to who you are and who you will be. You may not be as close to God as you are now without your past. The things you've done, they may be sinful and harmful, they may be horrid and you may hate them, but don't hate yourself. I cannot stress how important it is to confess your sin to God and repent (turn away from your sin), but once that is done, you have nothing to feel guilty about. Which brings me to my second point:
2. You should not feel guilty because you cannot change your past. You can regret what you have done, but feeling guilty will never change what you have done, but it will change what you do. If you feel guilty, you may think you are unable to change, and you will continue in your ways until you fall from under your guilt. What you have done is unchangeable: what you do about what you have done is not. Depending on the situation, you may or may not be able to make seemingly "large" changes, but you can always change. The first step is to confess your sins to God, and then make sure you don't fall where you fell before. And if your sin affected anyone else, make it right, or if it is impossible, try to the best of your ability to make it better. Regret what you've done, but don't feel bad-rejoice that you are saved by God. Use your regret to keep you from sin, not to make yourself lest resistent to it.
3. And this reflects my first two points: You should not feel guilty because you are FORGIVEN! If we confess our sins, he is faithful and just to forgive us our sins and to cleanse us from all unrighteousness.
(1 John 1:9 ESV)
“I, I am he who blots out your transgressions for my own sake, and I will not remember your sins.
(Isaiah 43:25 ESV)
The Bible stresses that we are FORGIVEN, and our sins are FORGOTTEN. We are FREE, our sins are FORGIVEN, our trespasses FORGOTTEN, and this lasts FOREVER. that is my motto. If we are still guilty, we tell ourselves that God cannot forgive us, that His grace is not sufficient and we are not cleansed. No, WE ARE PURE! WE ARE RIGHTEOUS! I cannot stress this more!
So if you feel guilty, take time to search the Scriptures. I'd recommend the book of John.
And be set free.