E.D.
I completely understand. I had the same problem. I had PPdepression which caused me to lose my temper easily, and kids look to us to know how to deal with stress. I started by being honest. I sat down and discussed how our family feels when we are yelling a lot. then i owned up to it, apologizing for my behavior and said that i have a hard time not yelling and asked my kids for their help. (trust me, kids are more willing if they are helping you than being told they need to change) we made a family goal of speaking nicely, and reviewed that goal each week in "family council". then we would help each other with our yelling. also, one thing that has worked like a charm: there is a movie, it's a cartoon veggietales, called "larry boy and the angry eyebrows". my kids are familiar with it, so whenever we are angry and yelling, someone in the faily says, "make your angry eyebrows fly away" and the person is required to make an action with their index fingers next to their eyebrows, with them "flying away", it always makes them smile, and ends the anger. good luck, it's going to take a while, but these things can help!