Let it happen. Never ever say something to that person you are angry at. Just like you he or she has other reasons. So let it go. Time fixes everything
Never let your emotions control your actions, this is what is called end of friendship or whatever. Think once one day he or she might be the person you need the most.
Sit in a lonely place and try to understand why? Just consider his situation. It will help you to understand easier
Distract Yourself with Exercise
Find a Safe Haven & Discuss Your Anger with Someone Trustworthy
If you have a good habit of listening to music well use it.
Last & the hardest is, after sometimes go and say sorry even if your are not guilty. It will make you feel better just to know that your heart belongs to a good person