The man who goes into the wilderness on foot, stripped of all the devices of the illusion of fixed order, finds his assumptions to be much shorter lived. Afoot, cut off from the powers by which men change things, he has made himself vulnerable to change. Whether he intends it or not, the wilderness receives him as a student. And what it begins to teach him is how to live beyond his expectations; if he returns often and stays long perhaps it will teach him to live without expectations. It will teach him the wisdom of taking no thought for the morrow — not because taking thought is a bad idea, but because it is not possible; he doesn’t know what thought tomorrow will require.
–Wendell Berry, from The Unforeseen Wilderness, p. 247