I'm going to stick with the adulthood theme, but this quote is going to have more to do with parenting. Ever since I've read this quote it has stuck with me. Partly, I think, because it comes from one of Robert Bly's books and mostly because I'm an active parent in the United States.
"J.B. Yeats, W.B. Yeat's father, wrote to his son after living two years in the United States, 'You know discipline is essential in every family. In Europe the children discipline themselves so that the parents can have a good time; in America the parents discipline themselves so the children can have a good time.'" [Robert Bly, Pg.38, A little Book on The Human Shadow.]