It's wasn't a kidney stone, but oh, the pain!
I don't know about you, but when I pass another cyclist, I make a point of dropping them pretty quickly if I can. I do this because I hate it when somebody deems it necessary to pass me only to slow down and block my progress once they have done so. Sometimes when I'm kind of pumped up in the middle of a ride, I'll pass somebody going almost as fast as me. That is the worst, because then I feel obligated to kill myself rather than take a breather and allow them to pass me back. I get more exercise, but I always feel a bit stupid for caring whether I get overtaken by them. I mean, who cares, really?