How do I forgive myself and find happiness again?

I had microcheated/cheated on my girlfriend. I had immediate regret and guilt from it and I told her. She has forgiven me but I can’t seem to forgive myself and move forward from it. I don’t feel happy internally. I’ve had these compulsions of breaking up with her in hope I feel better, but at the same time I have fear that I’ve let go of someone who I feel is very special to me.

Hm, make sure, it never happens again in a relationship? Work on it and do not run from it? Basically face the fear and become a better person.