This is just the straight truth. Say there's a man who makes a living upholstering electric chairs; well, he's got to be in favor of capital punishment, right? I mean, that's his bread and butter, his livelihood; he can't very well go around saying the death penalty amounts to cruel and unusual punishment or the state has no more right to take a life than anyone else. He'd be biting the hand that feeds him. Or there's another guy, he puts those little red rings around the baloney slices, and you ask him what religion he thinks elephants are, and nine times out of ten, he'd say, "Hindu, I guess, I never thought about it," or else, "Get the hell away from me, are you crazy?" But suppose his son was an elephant mohel, then he'd be like, "They're Jewish, of course. Everybody knows that." Suppose you ask a guy if parachutes made out of Bounty paper towels are practical. Well, he's naturally going to say no, unless he's just been thrown out of a plane with nothing but a parachute made out of Bounty paper towels. Then he's going to come back and say, "Why yes! Paper towel parachutes are top-notch, and the very best brand is Bounty. It's the quicker-picker-upper!"
So what you got to try to do is look around at all the stuff you believe. Now anything that's inconvenient, like it'd be nice if it wasn't true but it is, like - "even if I flap my arms really hard and give myself a twenty-story head start, I won't be able to fly" - like that you know is a fact, because if it'd be a lot nicer to believe otherwise. So things like, "I don't have the power of invisibility," or "it's a good idea to keep my mouth shut once in a while" - are almost certainly true because it's something you wouldn't want to believe unless you had to. Where you get into trouble is the stuff that feels good to believe. This is the stuff that maybe is just baloney if you thought about it seriously but you can't stop believing it because it feels so good to tell yourself it's true. I won't give you any examples of what these things are, but they're exactly the things you like believing the most because maybe that's the reason you believe it in the first place.
And if you don't believe me... well, there you go.