His boss gave him an axe and showed him the area where he supposed to work.
The first day, the lumberjack brought 18 trees.
“Congratulations,” the boss said. “Go on that way!”
Very motivated by the boss words, the lumberjack tried harder the next day, but he could only bring 15 trees.
The third day he tried even harder, but he could only bring 10 trees. Day after day he was bringing still fewer trees.
“I must be losing my strength”, the lumberjack thought. He went to the boss and apologized, 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…”