Once upon a time, a very strong woodcutter asked for a job with a timber merchant, and he got it. The pay was really good, and so were the work conditions. For that reason, the woodcutter was determined to do his best. His boss gave him an axe and showed him the area where he was supposed to work.
The first day, the woodcutter brought in 18 trees, and of course his boss congratulated him. Motivated by his boss' words, the woodcutter tried harder the next day, but he could only bring in 15 trees. The third day he tried even harder, but he could only bring in 10 trees. Day after day he was bringing in fewer and fewer trees.
The woodcutter thought he was losing his strength, and he went to the boss and apologized, saying that he couldn't understand what was going on. His boss then asked, "When was the last time you sharpened your axe?" Appalled by the question, the woodcutter harshly replied, "Sharpen my axe? I have no time to do that. I've been busy cutting trees."