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The most spiritual men, as the strongest, find their happiness where others would find their destruction: in the labyrinth, in hardness against themselves and others, in experiments. Their joy is self-conquest: asceticism becomes in them nature, need, and instinct. Difficult tasks are a privilege to them; to play with burdens that crush others, a recreation. Knowledge–a form of asceticism. They are the most venerable kind of man: that does not preclude their being the most cheerful and the kindliest.
Friedrich Nietzsche
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https://www.goodreads.com/author/quotes/1938.Friedrich_Nietzsche?page=6