Getting stuck in a particular way of understanding the world - whatever it is - is the cause of three major human diseases: The first one is seriousness, as in "dead serious." Second - Certainty is where people stop thinking and stop noticing. It's easy for certainty to sneak up on you. Even people who are uncertain are usually certain about that, too. "Are you sure enough to be unsure?" The third disease is importance, and self-importance is the worst of all. These three diseases are the way most people get stuck. You may decide something is important, but you can't get really serious about it until you're certain that it's important. At that point you stop thinking altogether.

The intellect, like an opera glass, should only be turned up to a certain point; if you screw it any farther, you see more hazily.