A farmer goes to his doctor complaining his penis is rubbed raw. The doctor nods knowingly and tells him he needs to stop jerking off so much. The doc says go out and get yourself a wife.

So the farmer does exactly that. He finds a woman, marries her. A few weeks pass and he goes back to the doctor with the same problem.

Doctor asks why are you still masturbating so much now that you have a wife. Farmer goes, she tries, but her little hands get so tired.