Man is at his furthest remove from the animal as a child, his intellect most human. With his fifteenth year and puberty he comes astep closer to the animal; with the sense of possessions of his thirties (the median line between laziness and greediness), still another step. In his sixtieth year of life he frequently loses his modesty as well, then the septuagenarian steps up to us as a completely unmasked beast: one need only look at the eyes and the teeth.
Friedrich NietzscheIt is only great pain--that slow, sustained pain that takes its time, in which we are, as it were, burned with smoldering green firewood--that forces us philosophers to sink to our ultimate profundity and to do away with all the trust, everything good-natured, veil-imposing, mild and middling, on which we may have previously based our humanity. I doubt that such a pain makes us 'better'--but I know that it makes us deeper.
Friedrich Nietzsche