A couple has a pair of twin girls, aged six years old; one was a pessimist, the other an optimist. Worried and hoping to help the girls regulate their emotions more, the parents bring the girls to a psychologist.
The psychologist first treats the pessimist, leading her to a large room filled with all manner of wonderful toys; the psychologist them treats the optimist, leading her to a room piled high with horse manure. The psychologist them leaves the girls alone for about a half hour, then goes back to check on them.
Upon entering the pessimist’s room, he’s surprised to see her sitting in the middle of the room, looking very melancholy. “Say, what’s wrong?” he asks. “Wouldn’t you like to play with these nice toys?” The girl sobs. “No! I might break them!”
The psychologist then goes to check on the optimist and is surprised to see her gleefully digging through the horse manure with her bare hands. “Say,” the psychologist asks, perplexed. “What are you doing?”
“Well,” the girl replies. “With all this horse manure, there must be a pony in here somewhere!”