Nicomachean Ethics X.1

We begin the final book with a short chapter. The initial remarks are straightforward and biologically accurate; even in the womb, a fetus will try to move away from a needle. Whether this "avoidance behavior" counts as 'feeling pain' or not is, however, debated still somewhat hotly; but the avoidance response occurs quite early. There is thus something very basic about the avoidance of pain, perhaps even pre- or proto-conscious as a drive; the seeking of pleasure is likewise basic. These must therefore be considered in an account of human ethics as they will be deeply influential.

After these matters we ought perhaps next to discuss pleasure. For it is thought to be most intimately connected with our human nature, which is the reason why in educating the young we steer them by the rudders of pleasure and pain; it is thought, too, that to enjoy the things we ought and to hate the things we ought has the greatest bearing on virtue of character. For these things extend right through life, with a weight and power of their own in respect both to virtue and to the happy life, since men choose what is pleasant and avoid what is painful; and such things, it will be thought, we should least of all omit to discuss, especially since they admit of much dispute.

So, what should we say about it? Aristotle begins as often by explaining what often is said about it. Some people say that pleasure is the good; others say pleasure is bad. Some who say so believe that, and others just think they ought to say it in order to guide people away from being enslaved by their pleasures. 

For some say pleasure is the good, while others, on the contrary, say it is thoroughly bad-some no doubt being persuaded that the facts are so, and others thinking it has a better effect on our life to exhibit pleasure as a bad thing even if it is not; for most people (they think) incline towards it and are the slaves of their pleasures, for which reason they ought to lead them in the opposite direction, since thus they will reach the middle state. But surely this is not correct.

This is not the first time the issue of pleasures and pain has come up; Aristotle discussed it before in II.9 (this is the 'Helen at the Gates of Troy' warning against pleasures, coupled with advice that you should be keen about driving them off) and again in VII.13-14. The latter concluded that there were some noble pleasures that are worthy of pursuing. There are good things that are good all the time, like philosophical reflection, kindness, and friendship; these are not to be avoided because they have no excesses. There are other pleasures that do admit of excesses, such as food and drink, but these should still be pursued because they are in fact goods as long as they are pursued within a rule and not to excess.

Since we've already discussed the matter it's a little surprising to find ourselves returning to the ground in the last book of the EN. Nevertheless, Aristotle has a lot more to say about pleasure, pain, happiness and politics. 

In any case, Aristotle is against lying to people about pleasure being bad for them in order to try to guide them away from it. This will not fool people, he says, but it will make them despise you because they can see you are saying something you must know is not true. 

For arguments about matters concerned with feelings and actions are less reliable than facts: and so when they clash with the facts of perception they are despised, and discredit the truth as well; if a man who runs down pleasure is once seen to be aiming at it, his inclining towards it is thought to imply that it is all worthy of being aimed at; for most people are not good at drawing distinctions. True arguments seem, then, most useful, not only with a view to knowledge, but with a view to life also; for since they harmonize with the facts they are believed, and so they stimulate those who understand them to live according to them.-Enough of such questions; let us proceed to review the opinions that have been expressed about pleasure.

This at least is good advice about which many remain mistaken; I can't recount how many times in my childhood and youth adults would fiercely preach against things like beer and sex, which they would then go home to enjoy. Nobody is fooled, and the speaker is discredited thereby: the youth who might have listened to him and learned a good lesson from him will instead now set aside anything else he says thereafter.