"Anger and depression and sorrow are beautiful things in a story, but they're like poison to the filmmaker or artist. They're like a vise grip on creativity. If you're in that grip, you can hardly get out of bed, much less experience the flow of creativity and ideas. You must have clarity to create. You have to be able to catch ideas."

David Lynch interview:
http://www.utne.com/2007-05-01/DeepThoughtsbyDavidLynch.aspx