Rude people stress me out
I can put up with most things but people being rude or just plain nasty really gets to me.
Unfortunately I am British and it doesn't seem to come naturally to me to say something to the offending person when I experience or witness rudeness. All that happens is that I stew inside about if for hors afterwards, wishing I had said something etc.
I am trying to stop this happening in the future by thinking through the situation in my head and trying to see all sides of the situation. Often it is possible to see why someone may have reacted rudely etc and this helps me let it go rather than let it stress me out.