How can I calm myself down, and make myself less irritable?

I'm 15. My parents are alcoholics. I already had a lot on my mind today. But right now, them being drunk is driving me crazy! They are just being annoying, and making me incredibly irritable. If I don't calm down I'll end up starting a fight because I'm so annoyed, which is something I really don't want to do. How can I calm myself down, relax, and become less irritable?