Whenever I'm feeling like my day could not get worse, I remind myself "Hey, at least you aren't pregnant."
When other people are whining to me about petty shit (I don't care that you're tired. god. shut up.) I usually say "Nothing puts a bad day in perspective like your pen-pal in Nigeria saying that he has to go, because the riot police are on the way and he has to be off campus before they get there."