William's wife started noticing how forgetful he was becoming. Being the concerned wife, she convinced him to see a doctor. William was a little worried when the doctor came in. Sensing his patient's nervousness, the first thing the doctor did was to ask what was troubling him.
"Well," William answered. "I seem to be getting forgetful. I'm never sure I can remember where I put the car, or whether I answered a letter, or where I'm going, or what it is I'm going to do once I get there, if I get there. So, I really need your help. What can I do?"
The doctor thought for a moment, then answered in his kindest tone, "Please pay me in advance."