QUIT YELLING

It's the summer of the horrible mommy... I tried to stop drinking coffee because it is not really good for my nursing baby and I'm sure it's leaching the calcium out of my bones, but I can't manage to quit yelling at my oldest son without it. Maybe I just can't keep up with him without it. Yesterday I declared we would have a day of no yelling. Anyone who yelled (including me) would go to their room for a time out. I went twice. I always wonder how we got into this habit as a family of yelling at each other. Maybe my husband started it--I remember when we were at dog training several years ago and they deteremined that he always shouted at his dog so that was what she responded to...he does the same with me and the kids. Now, everyone yells to get their point across. Someone is going to blast an eardrum here soon.
I read a short book called Raising Children Compassionately Parenting the Nonviolent Communication Way, way too advanced for my husband and too frustrating for me at the moment. How do you go back and change to damage you've already done? It seems that even if you one day decide to change, there are so many setbacks and unanticipated bouts of yelling that it doesn't do much good. I've got to keep pursuing it though. We had a really good day yesterday...so I'll declare another day of no yelling today. (What I really know if that, as always, if I wrote regularly, I wouldn't be yelling so much. Because I would have made my point somewhere and it wouldn't seem so urgent to force my point home.) Even dogs can learn new tricks...or maybe they just keep drinking coffee. Which is worse yelling or caffeine?