Pain and discomfort after a break-up is usually due to the feeling that you can't have what you want. It's selfish and all encompassing, but with time and space it wanes. Soon you are less melodramatic and your friends aren't rolling their eyes at your Facebook posts anymore. Then you run into the ex and that little bit of sadness creeps back in. Perhaps you spend the afternoon imagining that s/he pulls you off to the side, pins you against the wall with their body and explains between passionate kisses how they've realized how perfect you are together... Ahem... or something like that.
You know you are torturing yourself. You wish you could just get over it. You wish you didn't still want them.
Here's the deal though, if you truly love someone, it shouldn't be about what you want from them. Wanting them to love you/want to be with you, is essentially asking for them not to feel the way they feel, so that you can feel good. That's not love. If you truly want them to follow their heart, do what they think is best for themselves, then it is impossible to want them to be with you at the same time.
Want to know the best way to get over someone? Love them. Fully, unconditionally, love them. Wish the best for them and the rest of their journey wether or not you will be a part of it.
Love isn't about you, it's about the other person.