Just a quick clarification of the previous post. Not to put too fine a point on it, but I'd suggest that what Bradbury really means is not "Don't think" but rather: don't let thinking get in the way. Came across this observation along similar lines:
Artspeak always sounds like a bunch of twenty-dollar words used to obscure the artist's inability to articulate what he or she is doing.
It's like over-thinking when throwing a rock at a street sign. Don't think about it, just do it, and you hit the target.
Start thinking about the outfit you should wear while throwing rocks at street signs, or how your body moves while throwing the rock, or what rock should be thrown at which street sign, and you're gonna get a lot of misses.