Benjamin Young:

Sometimes when I am debugging a computer program I come across a situation where I think I understand the entire state of the computer, and there is no way that whatever bug is happening could actually happen. At these moments, I have to look around and worry: "Is this the moment when the universe loses its ordered behavior? Will the sun come up tomorrow? Are my friends popping in and out of existence this very moment? IS THIS WHERE IT ALL ENDS???" Then I think "oh, wait, that variable's not supposed to be zero," and go along under the laws of nature once more.