"An action prompted by the life-instinct proves that it is a right action by the amount of pleasure that goes with it: and yet that Nihilist, with his bowels of Christian dogmatism, regarded pleasure as an objection… What destroys a man more quickly than to work, think and feel without inner necessity, without any deep personal desire, without pleasure—as a mere automaton of duty? That is the recipe for decadence, and no less for idiocy…" [Referring to Kant, but is the basic point not fundamentally Epicurean?]
Nietzsche, Antichrist, 11 - http://4umi.com/nietzsche/antichrist/11