I went through a break up earlier this year. I was a wreck for a month, maybe longer. The lonliness is awful. I think it is a bit important to let yourself grieve and then MOVE ON. My therapist has told me not to hide my anger and hurt but get it out by writing what you want to say in your mind but then tearing it up.
Think about all the positive possibilities for your future. Stay busy with friends, get your feelings out, do something that makes you smile and happy! I used to think affirmations were silly but it really does help to reset your mind.(I'm having to do that now myself) It's better to tell yourself positive things that you will eventually believe than dwell in negative.
Stay strong.