694.
According to the obstacles which a force seeks with a view of overcoming them, the measure of the failure and the fatality thus provoked must increase, and in so far as every force can only manifest itself against some thing that opposes it, an element of unhappiness is necessarily inherent in every action. But this pain acts as a greater incitement to life, and increases the will to power.
695.
If pleasure and pain are related to the feeling of power, life would have to represent such an increase in power that the difference, the "plus," would have to enter consciousness. A dead level of power, if maintained, would have to measure its happiness in relation to depreciations of that level, i.e. in relation to states of unhappiness and not of happiness.... The will to an increase lies in the essence of happiness: that power is enhanced, and that this difference becomes conscious.
In a state of decadence after a certain time the opposite difference becomes conscious, that is decrease: the memory of former strong moments depresses the present feelings of happiness in this state comparison reduces happiness.
696.
It is not the satisfaction of the will which is the cause of happiness (to this superficial theory I am more particularly opposed—this absurd psychological forgery in regard to the most simple things), but it is that the will is always striving to overcome that which stands in its way. The feeling of happiness lies precisely in the discontentedness of the will, in the fact that without opponents and obstacles it is never satisfied. "The happy man": a gregarious ideal.
697.
The normal discontent of our instincts—for instance, of the instinct of hunger, of sex, of movement—contains nothing which is in itself depressing; it rather provokes the feeling of life, and, whatever the pessimists may say to us, like all the rhythms of small and irritating stimuli, it strengthens. Instead of this discontent making us sick of life, it is rather the great stimulus to life.
(Pleasure might even perhaps be characterised as the rhythm of small and painful stimuli.)