An older man was married to a younger woman.  After several years of a very happy marriage, he had a heart attack.  The doctor advised him that to prolong his life, they should cut out sex.

He and his wife discussed the matter and decided that he should sleep in the family room downstairs, to save them both from temptation.

One night, after several weeks, he decided that life without sex wasn't worth living.  So he headed upstairs.  He met his wife on the staircase and said, "I was coming up to die."

She laughed and replied, "I was coming down to kill you..!!"