A young apprentice applied to a master carpenter for a job. The older man asked him, "Do you know your trade?" "Yes, sir!" the young man replied proudly. "Have you ever made a mistake?" the older man inquired. "No, sir!" the young man answered, feeling certain he would get the job. "Then there's no way I'm going to hire you," said the master carpenter, "because when you make one, you won't know how to fix it.

Wisdom from the World According to Mister Rogers: Important Things to Remember (ed. 2006)