This quote is so very true, I have learned this time and time again. I am still working on this myself, but it's a must you have to work on, and I know this myself, and I am still working on it. Don't let your anger control what comes out of your mouth, ever.
Speak when you are angry, and you will make the best speech you'll ever regret. - Laurence J. Peter, 1919-1988