The thing in my past

What if the thing that happened in my past is something that I did, not something that was done to me?
Something really awful. Something I don’t want to share. (I haven’t killed or physically hurt someone, don’t worry. I got drunk and said some offensive things, and upset some people, people I don’t know, who are not in my life so I can’t apologise to them).
How do I manage to change that? How do I manage to make that mean something positive?
I can’t make it mean anything positive. If I do that, I lessen it, I condone it.
I can tell myself stuff like this: “It has made me humble” and “It has made me empathic to others who do wrong”. None of that is making me feel any better. None of that is shaking the belief I have that I have done a terrible thing and am therefore a bad person. I feel this in my core, in my soul, and any thinking I do to the contrary feels like I’m just pretending otherwise. I do ok for a while, and then I remember this thing I did, and I am overcome with bleakness.
There are a heap of other terrible things I have done, too. I have never been a victim of someone else. Nobody has ever hurt me. I have just gone through life doing a series of shitty things, and I don’t feel like I deserve any redemption, to be honest.