"Magic Cure for Impotence" joke

A man has been married to his wife for over 20 years and during the past 5 years he has been unable to obtain an erection. He feels just horrible because he is unable to have sex with his wife. He fears his wife may leave him for another man.
Out of desperation the man has gone to every doctor and expert in the area. Despite numerous tests and suggested remedies, no reason for his impotence can be found and no cure has worked.
The man decides to share his problem with his best friend. His best friend gets all excited and says, "I know who can help you! There is mystic and he was able to help someone else I know with the same problem! You must go see him!"
So the man takes his friend's advice and goes to visit this curious mystic. The man explains his problem, the mystic looks him over and says, "Ah, yes, indeed I can offer a temporary cure."
The man is just elated, he tells the mystic, "Whatever it is, please do it! I want to be able to have sex with my wife, please!"
So the mystic nods his head, does a strange dance around the man while murmuring odd sounds, claps his hands and says, "All done. Now, sir, you will be able to bring on an erection immediately upon counting to three: one, two, three. Do not count to three until you want your erection. Your erection will continue to last until the count of four is heard: one, two, three, four. After that, you will not be able to obtain an erection again no matter what."
The man is just so excited, he leaves the mystic and heads home. All he can think about is that tonight he will be having sex again and giving his wife the love session of her life. He cannot wait to surprise her with his eager hard-on that will last and last and last.
That evening, the man is lying in bed waiting for his beautiful wife to walk out of the bathroom and crawl into bed beside him.
"How much longer will you be?", he inquires in a lound voice from the bed.
"Almost done sweetie.", his wife responds from the bathroom.
The man gazes down at his penis and counts outloud: "One, two, three". Sure enough, his penis stiffens into a grand hard-on.
The wife then hollars from the bathroom: "Honey, what did you say 'one, two, three,' for?"