Some favorite passages (as I'm brushing up on my Aristotle for class):
"Happiness, then, is not found in amusement; for it would be absurd if the end were amusement, and our lifelong efforts and sufferings aimed at amusing ourselves. For we choose practically everything for some other end--except for happiness, since it is [the] end; but serious work and toil aimed [only] at amusement appears stupid and excessively childish. Rather it seems correct to amuse ourselves so that we can do something serious...for amusement would seem to be relaxation, and it is because we cannot toil continuously that we require relaxation. Relaxation, then, is not [the] end; for we pursue it [to prepare] for activity. But the happy life seems to be a life in accord with virtue, which is a life involving serious actions, and not consisting in amusement." (Nicomachean Ethics, Book X, Ch. 7)
"This is the true joy in life, the being used for a purpose recognized by yourself as a mighty one; the being thoroughly worn out before you are thrown on the scrap heap; the being a force of Nature instead of a feverish selfish little clod of ailments and grievances complaining that the world will not devote itself to making you happy. And also the only real tragedy in life is the being used by personally minded men for purposes which you recognize to be base. All the rest is at worst mere misfortune or mortality." - George Bernard Shaw (in the preface to Man and Superman, I think)
"Of one thing I am certain – we are not here in order to have a good time." - Wittgenstein (attributed by John King, see here)
I'm thinking pretty hard about Aristotle's remarks about study/contemplation, and may take another crack here soon at how Book X fits (or doesn't) with the rest of the NE.