Inspiration is like perspiration. It tends to strike at the most inopportune of times.
It has been often said that writing is 99 percent perspiration and 1 percent inspiration. In my experience, this is true. But, in my opinion, it is useless without that 1 percent. It's like an engine without fuel -- can't get anywhere without it. Or like a lighthouse without a light on top -- doesn't guide anyone in to home or safe harbor.