OK but I want you forgive yourself what about me? (I have no idea why)

I have also hurt my ex girl friend for example. I took alcohol and insulted her. She cried and ran away.

Now looks like accusing myself is a good idea. But it is not. My ex doesn't even remember the issue its was 15 years ago. How to forgive myself? What is the excuse? There is only one and very good excuse. I HAVE NO IDEA WHY THIS HAPPENED. (not because of alcohol it was just one beer).
It was a random accident caused by previous events in my life, how they were interpreted in my brain, etc. When you look this way it is impossible to judge me neither. In addition, when you accept this you can easily apply to others and stop judging them. Impossible to judge.

3dnow