My friend Ian talks about "refilling the well," which I think fits much better. Think of the well as potential for creativity. You've got lots of passion for a story, lots of ideas and all that fancy jazz. The well is full. Then you're 50,000 words into a novel and running on empty. Your well needs refilling. This will happen differently for each writer: some need to read their favorite book for the billionth time; others need to people watch; some need to watch their favorite television show or movie and think about its character arcs or themes; others need to write something shorter--poetry, maybe, or just some freewrite scribbles; others still need to get away from writing for a while, maybe by drawing or knitting or getting lost on Tumblr for a few hours. Take the time to do this so you don't run yourself into the ground. When you've refilled your creativity well, you can return to your project or start a new one, as the case may be, with a renewed zest for your craft.