A father gave his son a bag of nails and told him to hammer one into the fence every time he lost his temper. Over several weeks, the boy was able to control his anger better and hammered fewer nails each day. When he went a full day without losing his temper, the father had him start pulling out a nail each day. Eventually, all the nails were removed. However, the father showed the son that the fence was still damaged from the holes left by the nails, telling him that hurtful words can similarly leave lasting wounds, even if apologized for.