Food for thought for the new year: two versions of a lecture on creativity by John Cleese, the silly-walking Monty Python and Fawlty Towers star. The first (and stronger) video is a full-length 1991 talk. The second is from the 2009 Creativity World Forum and may just be an excerpt of a longer presentation.
“You cannot be playful if you’re frightened that moving in some direction will be wrong, something you shouldn’t have done. You’re either free to play or you’re not. As Alan Watts puts it, you can’t be spontaneous within reason. So you’ve got to risk saying things that are silly and illogical and wrong. And the best way to get the confidence to do that is to know that while you’re being creative, nothing is wrong. There is no such thing as a mistake, and any drivel may lead to the breakthrough.” — John Cleese
You also might want to check out this Slate article, which picks up on one of Cleese's points, that a lot of people — e.g., bosses and teachers — don't actually like or encourage creativity.