(This is an old joke but its meaning is still relevant) A family had twin boys whose only resemblance to each other was their looks. If one felt it was too hot, the other thought it was too cold. If one said the TV was too loud, the other claimed the volume needed to be turned up. Opposite in every way, one was an eternal optimist, the other a doom & gloom pessimist.
Just to see what would happen, on the twins´ birthday their 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, I´ll have to read all these instructions before I can do anything with this stuff, I´ll constantly need batteries, and my toys will eventually get broken." answered the pessimist twin.
Passing the optimist twin´s room, the father found him dancing for joy in the pile of manure. "What are you so happy about?" he asked.
To which his optimist twin replied, "There´s got to be a pony in here somewhere!"