Have you dealt with guilt in therapy? How have you gone about it? Did you find any relief?

L and I are dealing with this topic right now. She sent me this article differentiating between guilt and regret. I have realized that I don't just have guilt, but some of the things are actually regret.
Guilt vs Regret in Grief

I'm scared to go down this path with L. I've never dealt with this. It has caused me a lot of pain and self-loathing. I'm scared. And I don't feel like I can or deserve to be free of this.