From Communitelligence.com comes this multipurpose anecdote:
Once I was trying to fix a toilet and water began to blast upward from a fitting. The building Super, who was watching me, commented, “You know the difference between a professional plumber and an amateur?”
“No,” I said, frantically searching for a towel.
“The professional makes as many mistakes as the amateur,” he said, swinging a wrench onto the main valve and closing off the fountain, “The difference is, a professional fixes them faster.”