Tips to forget about, forgive, and move on from ex?

It's been way too long and I'm still thinking about him. He even has a new girlfriend and I haven't been able to completely move on. I was able to put him out of my mind for a while, until I found out he has a new girlfriend, and all the past pain came back. Now I'm back to thinking about him and how he is doing everything we used to do with his new girlfriend. I really just want to forget about him and be able to move on with my life.