There once was a little boy with a bad temper. His father gave him a bag of nails and told him that every time he lost his temper, he should hammer a nail in the back fence rather than take it out on other people.
On the first day, the boy drove 37 nails into the fence. As the days went by, though, the number of nails gradually dwindled down. He discovered it was easier to hold his temper than to drive those nails into the fence.