Like they say its important to have an open mind, but not so open your brain falls out.

I pays to know what you believe, right up to the point where the evidence that you are wrong presents itself. Then continuing to believe, not matter how "steadfast", "committed", "optimistic" or "principled" you claim to be, is gonna crawl up your leg, and bite you right in the tender bits.

Which means that the more important the belief is, the more paranoid you have to be about it. Because otherwise, you will be clinging desperately to it, even when it goes over the cliff.