http://www.ted.com/index.php/talks/eliz ... enius.html
Author Elizabeth Gilbert talks about how creativity and serious mental illness tend to go hand-in-hand, and explains the main reason she thinks this is: Because we consider artists to "geniuses" (in the sense of people) rather than merely receiving genius from nature, the divine, etc., the way that the Greeks and Romans (and I'd add: Indians also) used to, with the idea of muses, daemons, etc..
I've had this view for a long while given my own experience with writing music. That is, I've noticed it is not possible to consciously write music. The only way music or any art can be created is with a kind of unseen inspiration that cannot be taught, captured, or explained.
This, by the way, is also a large basis for my anti-copyright views. You can't say an artist is "creating" anything, with tools, but rather, nature itself is creating and the artist themselves is merely a tool.