Via Proof with out Words:

Our need for consistency is stronger than just about any other intrinsic need we have. People will behave in a manner that is consistent with their previously existing self-concept, even when this behaviour is unrewarding to them otherwise. - Prescott Leaky

http://video.ted.com/assets/player/swf/EmbedPlayer.swf

A Japanese artist was commissioned by an American to do a paining. The completed work had, in a lower corner, the branch of a cherry tree with a few blossoms and a bird perched upon it. The entire upper half of the painting was white. Unhappily, the American asked the artist to put something else in the painting because it looked, well, so bare. The Japanese refused the request. When pressed for an explanation, the artist said if he did fill up the painting, there would be no space for the bird to fly.

http://prezi.com/bin/preziloader.swf