I was in the same position a while ago with a girl that I broke up with around last year.
Aside from a few months of depression, I tried talking with other girls.
Try to get with a different girl, or just flirt. Not to long after I started seeing other people I stopped caring for my ex, then again she treated me like shit.
It depends on the situation of the break up I think.
But if I were you, just try talking with other girls.
It might be hard considering you still have feelings for her, and that's understandable.
If it doesn't work, don't push on that idea.
I mean all I really did was talk to more girls and play a hell of a lot more video games then I stopped caring for her.
The more you dwell on missing her, the harder it gets.
It's a tough situation, it really is.
However you decide to go about the problem, I wish you the best of luck.