Imagine you're on a date and you're telling a story. It's a long one, but you know it's a winner. Everyone always loves this story. Three quarters of the way to the punch line, you notice a shift in your date's behavior. She's glancing at the door, bouncing her leg or messing with her hair. Does she want a cigarette? Does she need another drink to quell the anxiety? Has she been hit with a bout of explosive diarrhea?
Moments like these separate perceptive and considerate people from torturous, self-indulgent-asshole ones. The first will recognize the proper social cues and say something like, "Hey, let's grab another drink, and I'll finish this in a minute." The latter, however, will continue endlessly flapping their tight red gums, concentrating on themselves and their immediate needs.