I feel if I do not get the last word or insult in- then I look weak and defeated. I feel disgusting afterward. Please help.
I think that this is an untruth, that you look weak and defeated if you don't get the last word in. I sympathize with your situation! It's about self control, I guess, and knowing when you need to walk away. You're not in easy circumstances, dealing with customers, but if they are your bread and butter, allowing them the last word might be worth it. It sounds like you are getting defensive, and so maybe you need to look at that in therapy.