How do you control your temper?

I have a very bad temper when I am tired, which is a good 90 percent of the time. I recognize when I am being too short or when I get mad at stupid things, but I can’t stop it. How do I take control of my temper? I always regret getting mad and yelling at my son, because I know if I wasn’t so sleepy I wouldn’t have gotten mad at him for a lot of things. Help!!