Years ago, during my misspent youth as a physics major at the University of Copenhagen, there was a notorious Angry Man. His name was Arne, but everybody used to call him "Vrede Arne" (Danish: "Angry Arne").
The story goes that Arne once wasn't so Angry. He was actually a likeable, intelligent young man. However, somewhere along the way something went wrong. Nobody knows what - perhaps not even Arne himself. Arne started flunking courses, until he was finally relegated.
This didn't stop him showing up. It was really rather sad. He'd go around, staring with a surly mien at passersby in the hallways. He'd sit in the cafeteria, playing chess against himself (and getting into terrible arguments with himself - the only person I've ever seen do this).
Arne had long since developed irregular grooming habits, and become something of a stranger to the virtue of bathing regularly. His presence at lectures occasioned a curious phenomenon: I've seen a three-or-four-seat cordon sanitaire of empty seats around Arne, in an auditorium filled to bursting.
Arne's behaviour became more and more erratic, until finally he was taken away (kicking and screaming) by the police, presumably for a stay at a mental institution. He never came back to the University, that I know of - but I still see him on occasion, in the street. He's taken to bathing and shaving, and he doesn't look so Angry anymore.
Is there a moral to this story? I can't tell. Perhaps it is this: When you meet the Angry Man, think to yourself that once, he wasn't Angry. Then think about what it would take for you to end up as Angry as him.