Fred Sampson shares a few QOTD to make a political jab (And yes, Fred, I did like the funny, too). They struck a different chord for me, though, based on a recent read, Dietrich Dorner's The Logic of Failure, which drew may attention from its mention in Joel on Software...
Bertrand Russell. "The whole problem with the world is that fools and fanatics are always so certain of themselves, but wiser people so full of doubts."
John Kenneth Galbraith. "It is a far, far better thing to have a firm anchor in nonsense than to put out on the troubled sea of thought."
Dietrich's book explores how poorly we tend to handle making decisions. Two commonalities that arise from his data are that those who tend to make better decisions often have more doubt about their decisions, and that poor decision makers will often concentrate on nonsense (or irrelevant details) rather than attempt to tackle the larger, more important issues. I'll have to post some more of my thoughts about this book sometime...