One man challenged another to an all-day wood chopping contest.
The challenger worked very hard, stopping only for a brief lunch break. The other man had a leisurely lunch and took several breaks during the day. At the end of the day, the challenger was surprised and annoyed to find that the other fellow had chopped substantially more wood than he had.
"I don't get it," he said. "Every time I checked, you were taking a rest, yet you chopped more wood than I did."
"But you didn't notice," said the winning woodsman, "that I was sharpening my ax when I sat down to rest."