A 97-year-old man comes to his doctor looking depressed.

He says, "Doc, I think I'm impotent."

The Doctor sits him down and begins the standard speech he gives to senior citizens, about how as the body ages bodily functions slow down and it is completely normal to suffer some decrease in sexual desire, how the man shouldn't worry or become upset about it, but should just relax and things will probably be completely fine and blah blah blah.

Finally the doctor asks, "When did you first begin to think you were impotent?"

"Three times last night, and again this morning."