It seems really hard and impossible to get over that person at first. But just give it some time, that always helps. Just have in mind that whatever happened, he or she is not worth it and you werent meant to be together and it wouldve happened sooner or later anyway. Another really helpful thing is listening to break up songs like ridin solo or something.
When I broke up, or was broken up with, I loved the song with words to the effect of: I'm down, but I'm not out. There's also a poem that has the phrase, my head is bloody but unbowed. Tell yourself you are stronger than this, and it's not going to beat you. Be firm. Remember Desiderata: (I'll paste it below because it's long, but it will help you, I think.)
Get rid of the things that make you think of that person so it doesn't make you sad ..walk the opposite way they do like if you past them a lot go a different way they do, start hanging out with more people they will keep your mind off of that person. keep yourself busy don't just sit around or else they will come to your head again