Terry Pratchett, I Shall Wear Midnight

"If you do not know where you come from, then you don't know where you are, and if you don't know where you are, then you don't know where you're going. And if you don't know where you're going, you're probably going wrong."

"Preston, I don't think this creature could ever find its way into your head. Quite apart from anything else, it seems pretty crowded and complicated to me."