How do I forgive myself for mistakes I made in my last relationship?
I am really sorry to hear that you are struggling with guilt and hurt from a previous relationship. It sounds like your brain is on overdrive trying to help drill in the lesson that you learned and prevent you from not acting like that again in the future. We feel guilt when we violate our own morals. It may be helpful to reflect on what part of your actions violated your morals, to help you understand where you need to change. It may also be helpful to think through what you have done to correct this. Have you apologized to your Ex-Partner? Is this something that would be helpful for them? If it is not helpful for them and only self-serving, do not apologize to them. Figure out some alternatives. You can write your apology letter out and not send it. It may also be helpful to reflect on the ways that you are not violating your morals anymore. The ways you have learned from your behavior and are choosing not to repeat it. And actually, remind yourself that you are choosing different actions now! You are choosing to be different and show up different. That is huge and hard work.
It can be important to share your story with a trusted person (a friend, family member, mental health professional, etc.). Someone who can show up for you and not add to the guilt or make things worse, but really listen and hear the ways you are feeling your guilt. It is really hard to show our guilt to other people, our instinct is to hide it away and it takes a lot of courage to show it to others. When we do the opposite of what we feel like we should do, we may actually end up finding what we need.
The last thing I want to offer you is a reminder to be compassionate with yourself. You have done the hard work to identify how you harmed someone and now you need to do the work to forgive yourself. There was a reason that you acted that way and I don't think it is because you just wanted to hurt someone, or else you probably wouldn't feel guilty. I suspect you were doing the things you thought were right at the moment, but realized later you didn't want to be doing. You are not alone in feeling guilt. We're all doing the best that we can at any given moment and we learn more and decide to readjust our behavior. It is not easy to get through that learning and relearning. I wish you luck in your journey to self-forgiveness.