When the muse disappears

What happens to a writer when the inspiration and excitement of creation vanishes? How do you recover the desire to fill the page with all the wonderful things that used to come so easily to your mind? How do you dispel the wonderful feeling of freedom that comes when that forbidden thought sneaks into your mind: "I don't have to do this anymore!" Is there a time that it is finally okay to say "Enough"? Does a serious writer ever really get to that point? Or is it just a temporary lull in good judgment, or a time of exhaustion of mind and body that brings it on? So many questions. Does anyone have any answers?