PFM, do you have a therapist? Talking about the incidents when you were young and letting the feelings out will help to stop the triggering up of these incidents. These stuffed feelings are ripe for being triggered. If you can unload them they can't be triggered up. Talking to a T about feeling like that little child again will help also. When you do feel like that little child you can tell yourself that this is being triggered up from the past and you are not really that little child anymore. It is just the triggered up feelings that make you feel that way.

Any chance you can take some kind of self defense class or martial arts?

And try to remember that people get mad at customer service all the time over the littlest things so it isn't as sinister as it feels. They are just irritated and their anger belongs to them. It isn't really about you.