A bad habit
I overheard a friend telling his pal, "I can't break my wife of the habit of staying up until 5 in the morning.""What is she doing?", the pal asks."Waiting for me to get home."

An accountant is having a hard time sleeping...
An accountant is having a hard time sleeping and goes to see his doctor."Doctor, I just can't get to sleep at night." "Have you tried counting sheep?""That's the problem - I make a mistake and then spend three hours trying to find it."