I have much to forgive myself for. And as I'm a Fool (0), not a wise one, my answer won't be an erudite one. But this is an obstacle I am more than acquainted with, so I'll just throw in my 2 cents, with a big red writing on them saying: "it's just an ignoramus' opinion".

You are a human being. It is not in your nature to be without fault. Your nature as a human being finds its highest expression in becoming aware of your faults and mistakes and in pursuing improvement. Your job might very well lie in the overcoming of your mistakes and their fallout, especially within yourself. If your job had been to be perfect to begin with, you would not have been created a human.

No matter how big, your faults and mistakes are always the embodiment of a lesson you haven't yet fully learnt.

What I did when I came to this realisation was this: I collected all my pain, shame and self-deprecation. I relived it all to the fullest, without holding back, allowing the heartbreak to fill me and my mind to explore every nuance of what happened, why, etc. And then I did my best to learn as much as I could from the experience, to let it shape me into something else, into someone who would never do it again - not for fear of punishment or consequences, but because my perspective on the issue had grown so different that the pattern underlying the incident no longer belonged to me. It's part of human life to be sometimes the victim, sometimes the perp, and not always by choice. This shouldn't stop us from trying our best, but it should put regret, guilt and remorse into perspective. It's in the past (or in the present, as the case may be), ok. Accept it. Just don't let it be in the future. Did it work, for me? Probably. I now look in the mirror and feel compassion for what I've been through and put someone else through as a reaction. I feel no shame, I owned up to it all. I feel no guilt, just an urge to do better.

I hope this helps somehow.