"Think of what you're saying, you can get it wrong and still think that it's all right." from some song by John Lennon and Paul McCartney. anyway, this got me thinking about how many times I've though I've really understood something, or was absolutely sure that I was correct about something when it turns out that I had it completely backwards or I was thinking pure garbage. This is incredibly frustrating and dangerous. It's one thing to know you're in the wrong - at least you know you have to keep searching for the correct understanding or solution. However, when you're damned sure you're absolutely correct, you can't pick up on your mistake. worst case for me was when I got the commutator laws completely wrong on a quantum mechanics test, but was so sure of myself that I didn't bother to check. how do you guard against this sort of internal sabotage?