Forgiving someone who isn’t sorry

I understand that I forgive people because I no longer want to feel resentment and anger towards them.

But I don’t know how to actually do this. I keep having the thought that person X “owes me” and that they are in debt to me forever for what I did for them, and they just don’t agree. They aren’t sorry.

I can see that my thoughts cause me pain, but I am just so mad that I can’t let it go. I think I just feel like I want my feelings to be justified and validated, I want to be recognized for the pain they put me through but they don’t care.

I don’t even know how to begin to forgive this. Any idea on where I can start?