Get over it & move on
I know it sounds harsh, but in life nothing is easy. You can not let anyone or the thought of anyone hold you down. You need to be the best you can be because you are only given one life, why would you for a second let someone take away your ability to enjoy each day. Yes, it's hard to let go of the feeling of always having someone there, but in the end you are only going to be left with yourself, so you mind as well embrace it.

Go out with friends and have fun
You will only get upset if you sit alone and let your mind wonder on the breakup. If you keep yourself entertained with your friends you will realize you don't need a boyfriend to make you happy. Going out and making memories will last longer then any stupid boy will last. Ew. boys. don't need 'em.