It is frustrating, that's for sure, and especially when you clear your schedule and make time for something that is really quite important.
I find that it is especially bad when I have other things on my mind. When something just ridiculous happens and I am not stressed out, I can almost laugh it off and say "Here we go again", but when I am under pressure the new burden seems all the more unreasonable and infuriating.
One day I told my assistant that I just felt like sticking my head out the window and screaming: He told me "Excellent idea"! Perhaps I should have done it