without being sure of something, we can not begin to think about everything elses

Regret doesn't remind us that we did badly, it reminds us that we know that we could do better.

both doubt and certainty are as contagious as the common cold

wrongness always seems to come at us from left field - that is, from outside ourselves. But the reality could hardly be more different. Error is the ultimate inside job. Yes, the world can be profoundly confusing; and yes, other people can mislead or deceive you. In the end, though, nobody but you can choose to believe your own beliefs.

doubt is a skill. credulity ,by contrast, appears to be something very like an instinct

Error ... is less an intellectual problem than an existential one - a crisis not in what we know, but in who we are. We hear something of that identity crisis in the questions we ask ourselves in the aftemath of error: What was I thinking? How could I have done that?

We're terrified of not having the answers, and we would sometimes rather assert an incorrect answer than make our peace with the fact that we really don't know.