There was a boy who was always losing his temper. His father gave him a bag full of nails and said to him, "My son, I want you to hammer a nail into our garden fence every time you need to direct your anger against something and you lose your temper."

So the son started to follow his father's advice. On the first day, he hammered in 37 nails, but getting the nails into the fence was not easy, so he tried to control himself when he got angry. As the days went by, he was hammering in fewer nails; and within weeks, he was able to control himself and to refrain from getting angry and from hammering nails. He came to his father and told him what he had achieved. His father was happy with his son's efforts and said to him, "But now, my son, you have to take out a nail for every day that you do not get angry."

The son started to take out the nails for each day that he did not get angry, until there were no nails left in the fence.