The easiest belief to protect is the one you never allow yourself to test.

An untested belief is undefeated, and that is not the same as being right. Keeping something away from examination preserves it perfectly and leaves you unable to tell whether it is true or merely unchallenged. The beliefs people guard most carefully tend to be the ones they suspect would not hold up, though they rarely put it that way to themselves.

Take something you hold and have never seriously questioned, and spend an hour on the strongest case against it. Not to abandon it, only to see how it does. Beliefs that survive that come out stronger, and the ones that do not were costing you something.