The story is told of a father who had twin sons. One son was an optimist, the other a pessimist.
On the twins’ birthday, while the boys were at school, the father loaded the pessimist’s room with every imaginable toy and game. The optimist’s room he loaded with horse manure.
That night the father passed by the pessimist’s room and found him sitting amid his new gifts crying bitterly.
“Why are you crying?” the father asked.
“Because my friends will be jealous, and I’ll have to read the instructions, and I’ll constantly need batteries, and my toys will get broken,” answered the pessimist.
Passing the optimist’s room, the father found him dancing for joy in the pile of manure. “What are you so happy about?” asked the father.
To which the optimist replied, “There’s got to be a pony in here somewhere!”
I found this story over a decade ago in the internet. Tracking the source is apparently difficult. See: