How important is happiness?

The Washington Post today has an article based on the work of Daniel Kahneman suggesting that Americans in higher income groups spend less time relaxing and having fun than do people in lower income groups, and therefore they are happier.

The ancient Greek definition of happiness was the full use of your powers along lines of excellence.
John F. Kennedy

Of course, it is hard to be happy if you are ill, in pain, or suffering from the extreme aspects of poverty. But there seems to be a fair amount of evidence that once basic needs are satisfied, there is little gain in happiness with added income or wealth.

Still, I find it hard to accept that happiness is identified with having fun and relaxing.

Are there not two kinds of happiness. On the one hand there is a short term emotion which we all know, when things are going especially well and we feel satisfaction. A child born, an obstacle overcome, a friend who has succeeded. There is also a happiness as a more general satisfaction with life, which I think may come from overcoming expectations "of more" and satisfaction with what is, what has been, and what is likely to be.

It seems to me it is pleasant to be happy, and perhaps fortunate to be happy, but one might better aspire to be useful.