I know how you feel.
I work in food service.
One day I got really mad at a customer who called back to complain, he yelled at me for about five minutes before I snapped and yelled something like "well maybe we are having a really cr*ppy day here today and if you would shut up for a minute I would find a way to fix your order!" then I hung up.
My co-workers were all shocked, they had never seen me yell at someone before. In fact I'm quietest one there and always say "please", "thank you" and "have a nice day".