There's no magical recipe. It's hard and you are going to have to through it one way or another. Time is the best solution. However, to make the suffering less, depending on your personality, there are things you can do. Artistic activities, exercise, spending time with loved ones, adopting an animal in need from a shelter, .... But for your own sake, please don't rush into another relationship. Honestly it does help forgetting but it can cause much bigger problems. Meanwhile, find out why exactly are you mad. Is it because you feel jealous? Cause in many cases that's the case and it creates a feeling of worthlessness. If that's the case, remind yourself that he cheated because he was an idiot not because you weren't good enough. In any way, cheer up. Things happen for a reason in life. Believe me, you're going to be much happier before you even know it.
Spend 10 min a day by your self to cry About it and not a minute more. After a bit you will notice that you don't need 10 min anymore and soon it will fade. And remember the ones who cheat are the ones with the personal issues not you. No matter what it's not your fault, he chose to go somewhere else to fix a problem instead of coming to you.