Holes in the fence

There was once a boy with a bad temper. His father gave him a bag of nails and told him that every time he lost his temper, he must hammer a nail into the back of the fence.
On the first day the boy drove 37 nails into the fence. Over the next few weeks, as he learned to control his anger, the number of nails hammered daily gradually dwindled.
He discovered that it was easier to hold his temper than to drive nails into a fence. Finally, a day came when he didn’t need the hammer and nails at all. Proudly, he went to tell his father. This time the father suggested that each day he kept his temper, the boy should pull out a nail from the fence.
The days passed, until eventually the boy was able to tell his father that at last all the nails were gone. The father took the boy by the hand and led him to the fence. “You have done well — but look at all the holes in the fence! It will never be the same again. When you say things in anger, they leave a scar just like this one. You can put a knife in a man and draw it out. It won’t matter how many times you say I’m sorry, the wound is still there.”