If I Should Die Before I Wake

In this novella, or very long short story, a mild-mannered mob accountant goes on the run after he embezzles millions of dollars from his boss. He is chased across the country by a hired killer, and is forced to hide out in cheap, out of the way motels. He dreads the day the gunman will catch up with him, aware that he doesn't have the strength to defend himself. Except when he sleeps, at which time he dreams that he is the fearless hunter, and no longer the cowering prey. As the real killer closes in on him, the line between his dreams and his waking life become blurred.