Most Helpful Guy
Sometimes there's good reasons, if someone makes you unhappy through some behavior then really it should be up to them to know what they're doing, if they still choose to do it knowing it's causing a problem then it's not like you have to make a difficult choice coz they've made it for you. You've got to square it with yourself that what you're really sad about is that it's a shame your partner couldn't fulfill their potential as a person and you can't be with them.
Most Helpful Girl
You have to remember why you broke up with him. When I went through a bad breakup, I made a list of reasons I needed to stay away. You know how long it turned out to be without me trying? Three pages. My point is, someday your heart will understand that you couldn't ever be truly happy with him. There will always be good things to vouch for, but it's important to not forget about the bad things when you think of him.
It will be tough, but the sooner you start to face the pain head on, the better off you'll be and the sooner you are to being happy again. Keep a few loved ones close by to help you with this and to remind you why you need to stay away. Good luck.