Most Helpful Girl
Willpower and determination. You really just have to be determined to get back to a good life. You've got to have that willpower to get back to a regularly joyful life where internal peace isn't foreign.
One key thing is to stop entertaining situations where whoever/whatever you're trying to move on from keeps popping back up.
Most Helpful Guy
I recently broke up with my girlfriend of a year and a half and it took about 3 months to not be upset anymore. Not going to lie, I still think of her and the good times we had together.
Time is definitely the best factor. Over time you will learn that this person is not the only person you can be happy with. I suggest doing a few things: learn some lessons from your relationship, remember the good times, remember why you broke up, and find someone else that can make you happy (or be alone for a while if that's what you prefer). Main suggestion though - think about what you want in life other than her. (Ex. job, relationship, friends, etc...)