Once upon a time, a very strong woodcutter asked for a job from a timber merchant, and he got it. The pay was really good and so were the work conditions. For these reasons, the woodcutter decided to do his best.
　　 His boss gave him an axe and showed him the place where he was to work.
　　 The first day, the woodcutter brought 18 trees.
　　 “Congratulations,” the boss said. “Go on that way!”
　　 Being happy for the boss’ words, the woodcutter tried harder the next day, but he only could bring 15 trees. The third day he tried even harder, but he only could bring 10 trees. Day after day he was bringing fewer and fewer trees.
　　 “I must be losing my strength,” the woodcutter thought. He went to the boss and said sorry, saying that he could not understand what was going on.
　　 “When was the last time you sharpened your axe?” the boss asked.
　　 “Sharpen? I had no time to sharpen my axe. I have been very busy trying to cut trees...”