This is the question: what is a body capable of? What affects are you capable of? Experiment, but you need a lot of prudence to experiment. We live in a world which is generally disagreeable, where not only people but the established powers have a stake in transmitting sad affects to us. Sadness, sad affects, are all those which reduce our power to act. The established powers need our sadness to make us slaves. The tyrant, the priest, the captors of souls need to persuade us that life is hard and a burden. The powers that be need to repress us no less than to make us anxious or, as Virilio says, to administer and organise our intimate little fears. The long universal moan about life: the lack-to-be which is life… In vain someone says, ‘Let’s dance; we are not really very happy. In vain someone says, ‘What misfortune death is’; for one would need to have lived to have something to lose. Those who are sick, in soul as in body, will not let go of us, the vampires, until they have transmitted to us their neurosis and their anxiety, their beloved castration, the resentment against life, filthy contagion.
— Deleuze and Parnet, Dialogues II, p. 61-62.