I certainly wasn't raised to be rude to people.
I was in Tesco, at the self service, and was juggling everything and dropped something. No harm done. The sales assistant ran over making "squawky" noises and it really irritated me, I think because it made people turn and look which always flustered me.
So I (rudely) snapped, "All right, I dropped something, is there really any need to be so dramatic?"
This happened a lot when I was younger. I found myself being confrontational, surly and generally unpleasant in interactions with random people and it is starting to happen again now quite a bit.
Has anyone ever managed to successfully stamp this out of their character?