On his 70th birthday, a man was given a gift certificate from his wife.  The certificate was for a consultation  with an Indian medicine man living on a nearby reservation who was rumored to have a simple cure for erectile dysfunction. 

The husband went to the reservation and saw the medicine man. The old Indian gave him a potion and with a grip on his shoulder warned, "This is a powerful medicine. You take only a teaspoonful, and then say: "1-2-3.' When you do, you will become more manly than you have ever been in your life, and you can perform for as long as you want."

The man thanked the old Indian, and as he walked away, he turned and asked:  How do I stop the medicine from working?"

"Your partner must say 1-2-3-4,' he responded, "but when she does, the medicine will not work again until the next full moon." 

He was very eager to see if it worked so he went home, showered, shaved took a spoonful of the medicine, and then invited his wife to join him in the bedroom.  When she came in, he took off his clothes and said: "1-2-3!"   Immediately, he was the manliest of men. 

His wife was excited and began throwing off her clothes, and then she asked: "What was the 1-2-3 for?"

And that, boys and girls, is why we should never end our sentences with a preposition, because we could end up with a dangling participle.