Surely everyone has at least one thing that they can't handle.
Maybe you can do blood and guts and poo, but the smell of pee gets you? What is the one thing that messes you up? Did you know going in to school that it was going to be your weakness, or were you surprised when you ran out of the room the first time?
Mine is ortho. I can take all the nursing smells and sights, but I will hit the floor if I hear bones crunching or grinding. I can see them, no problem. But the chiseling/grinding sounds of ortho surgeries...shudder! Even fake TV sounds get me.