"A typically morbid being cannot become healthy, still less make itself healthy; for a typical healthy person, conversely, being ill can even be an energetic stimulant to living... This, indeed, is how that long period of illness appears to me now: it was as if I discovered life anew, myself included; I turned my will to health, to life, into my philosophy...
The years when my vitality was at its lowest were when I stopped being a pessimist: the instinct for self-recovery forbade me a philosophy of poverty and discouragement... How do you tell if someone has turned out well! By the fact that someone who has turned out well is good for our senses: the stuff he is made of is at once hard, delicate, and fragrant. Only what he finds conducive is to his taste; his pleasure, his enjoyment stops when the mark of what is conducive is overstepped. He guesses correctly what will heal harm, he exploits strokes of bad luck to his advantage; what does not kill him makes him stronger."
Ecce Homo