Well, literally, hearts can't break. Metaphorically, they can. So, I am assuming you mean metaphorically. Well, just find something to get your mind off of that someone. Go out with friends. Look at all of their bad qualities and convince yourself it was good that you broke up. Find someone new to like. There are so many possibilities. Good luck.
My heart is broken right now too. Just changed my number yesterday. Feeling a little lonely but what helps me is focusing on my goals and just thinking about myself to distract me from thinking about him. It helps and I'm starting to feel more powerful rather than weak and sad. I hope this helps you, and I hope you feel better too.
With time. Time is the best healer. Everything will get better in the future. You just have to forget everything that happened in the past, and move on. You can't keep dwelling on everything that DID happen in the past. You have a whole life to live, and one chance to make it a good life. Enjoy it while you have it.