Nice one...

Once upon a  time a very strong woodcutter asked for a job with a timber merchant, and he got  it. The salary 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 18 trees
"Congratulations,"  the boss said. "Go on that way!"
Very  motivated by the boss' words, the woodcutter tried harder the next day, but  could bring 15 trees only. The third day he tried even harder, but could bring  10 trees only. Day after day he was bringing less and less trees.  
"I must be  losing my strength", the woodcutter 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..."  

Moral  of the story:
Working hard  is not enough; one has to keep on sharpening one's skills.