how do I cope?

I've helped a lot of my friends through really painful breakups and friendships, and i noticed that a lot of people really care about what their EXes are doing when they shouldn't.

You guys seperated, no matter whose fault it was, you're now different people and the best course of action is to leave him alone and therefore leave yourself in peace. His success doesn't equal your failure, you can build yourself up just fine if not BETTER than him, and the only thing holding you back is your own mindset.

It's really painful to see someone who hurt you do better than you in life, i get that because i've been through it. But it NEVER should be something that brings you down. Use it as motivation. If they can do it then why can't you.

I also agree with what @Flint said, overthinking is a big curse in building relationships and will lead to you being unhappy.

Give yourself time, don't get into relationships out of emotion and loneliness. You should only attempt it when YOU feel that you're mentally ready for it and that you understand all the hardships that come with it. There needs to be mutual effort, mutual forgiveness and mutual care.