Pleasure has desire in it. Desire is pain. There is no satisfaction. So pleasure is pain.

Pleasure, or pain, is not only good, or evil, in itself, but the measure of what is good or evil, in every object of desire or aversion; for the ultimate reason why we pursue one thing, and avoid another, is because we expect pleasure from the former, and apprehend pain from the latter. If we sometimes decline a present pleasure, it is not because we are averse to pleasure itself, but because we conceive, that in the present instance, it will be necessarily connected with a greater pain. In like manner, if we sometimes voluntarily submit to a present pain, it is because we judge that it is necessarily connected with a greater pleasure.

If we are to have intense pleasures, we must also be liable to intense pains. The pleasure we love, and the pain we hate, but it seems impossible to have the former without the latter. Indeed, it looks as if the two must in some way alternate, for continuous pleasure is a stimulus that must either pall or be increased. And the increase will either harden the sense buds with its friction, or turn into pain. A consistent diet of rich food either destroys the appetite or makes one sick.

Pain itself is merely a consequence of the desire for pleasure, the desire t destroy, to annihilate; in its supreme form, pain is a variety of pleasure.

Pleasure wouldn’t exist without the sharp bite of pain. Even the brief flash of orgasm is too intense to be absolutely pleasurable

Pleasure, scarcely in one instance, is ever able to reach ecstasy and rapture; and in no one instance can it continue for any time at its highest pitch and altitude. The spirits evaporate, the nerves relax, the fabric is disordered, and the enjoyment quickly degenerates into fatigue and uneasiness. But pain often, good God, how often! rises to torture and agony; and the longer it continues, it becomes still more genuine agony and torture. Patience is exhausted, courage languishes, melancholy seizes us, and nothing terminates our misery but the removal of its cause, or another event, which is the sole cure of all evil, but which, from our natural folly, we regard with still greater horror and consternation.

Happiness consists in frequent repetition of pleasure

It is also suggested that the bad things in life are necessary in order to appreciate the good things, or at least to appreciate them fully. On this view, we can only enjoy pleasures (as much as we do) because we also experience pain. Similarly, our achievements are more satisfying if we have to work hard to attain them, and fulfilled desires mean more to us because we know that desires are not always fulfilled. There are many problems with this sort of argument. First, these sorts of claims are not always true. There is much pain that serves no useful purpose. There is no value in labor pains or in pain resulting from terminal diseases, for example. While the pain associated with kidney stones might now lead somebody to seek medical help, for most of human history, such pain served no purpose, as there was absolutely nothing anybody could do about kidney stones. Moreover, there are at least some pleasures we can enjoy without having to experience pain. Pleasant tastes, for example, do not require any experience of pain or unpleasantness. Similarly, many achievements can be satisfying even if they involve less or no striving. There may be a special satisfaction in the ease of attainment. There may be some individual variation. Perhaps some people are more capable of enjoying pleasure without having to experience pain and more capable of taking satisfaction in achievements that come with ease. Second, insofar as the good things in life do require a contrast in order to be fully appreciated, it is not clear that this appreciation requires as much bad as there is. We do not, for example, require millions of people suffering from chronic pain, infectious diseases, advancing paralysis, and tumors in order to appreciate the good things in life. We could enjoy our achievements without having to work quite so hard to attain them.

There is a pleasure which is born of pain.

We cannot be more sensitive to pleasure without being more sensitive to pain.

The inextricable way pleasure and pain are mixed up with each other in this world is a mournful fact to beings who are all the time striving for pleasure alone. In the ideal world there is no pain, no misery. There is nothing but happiness. But in our world pain seems to have been the original feeling, the first one to appear in the evolution of sentiency. Pleasure is a sort of after-thought, a secondary attribute of consciousness which developed later as an aid to pain in keeping living beings straight. Pain is a whip, a penalty. Pleasure is a reward or bribe. Pain is a curse. We are all the time trying to minimize and escape it. In an ideal world the inhabitants never have any impulses that drive them to improper acts. All their impulses are good. Every act is proper and right. Ideal beings need only to live and act in order to be happy. We are not ideal beings. Our world happens to be one affording almost unlimited opportunities for improvement.

My experience is that everything is bliss. But the desire for bliss creates pain. Thus bliss becomes the seed of pain. The entire universe of pain is born of desire. Give up the desire for pleasure and you will not even know what is pain. (…) for the sake of pleasure you are committing many sins. And the fruits of sin are suffering and death.

Pleasure is never as pleasant as we expected it to be and pain is always more painful. The pain in the world always outweighs the pleasure. If you don't believe it, compare the respective feelings of two animals, one of which is eating the other.

Pleasure causes us to do base actions and pain causes us to abstain from doing noble actions.