Why?

First, I honestly hate Facebook because you can see what your ex is doing even after you unfriend him. So my question is this, why in the hell does he get to be happy with a new girl and I am still hurting? I know I don't want him, but it still cuts me deep. Why is that? Yes, my issues have something to do with it, but I really just don't want to give a care at all. Please pray for me to just not care about him and her, and him altogether. I just want to let this all go completely. I do feel sorry for her though. He is still the same selfish person he was a few months ago, and I believe he will be until he takes time to work out his issues. I wish this would just be gone forever.