In his article In Praise of Melancholy, Eric G Wilson writes:

I for one am afraid that American culture's overemphasis on happiness at the expense of sadness might be dangerous, a wanton forgetting of an essential part of a full life. I further am concerned that to desire only happiness in a world undoubtedly tragic is to become inauthentic, to settle for unrealistic abstractions that ignore concrete situations. I am finally fearful of our society's efforts to expunge melancholia. Without the agitations of the soul, would all of our magnificently yearning towers topple? Would our heart-torn symphonies cease?

My fears grow out of my suspicion that the predominant form of American happiness breeds blandness. This kind of happiness appears to disregard the value of sadness. This brand of supposed joy, moreover, seems to foster an ignorance of life's enduring and vital polarity between agony and ecstasy, dejection and ebullience. Trying to forget sadness and its integral place in the great rhythm of the cosmos, this sort of happiness insinuates that the blues are an aberrant state that should be cursed as weakness of will or removed with the help of a little pink pill.

He goes on to talk about the role of melancholy in creativity. He's not advocating the kind of depression that can be self-destructive or dangerous to other people, but talking about a kind of sadness or melancholy that comes from the knowledge that we are essentially fractured ephemera, but which makes us appreciate what time we do have and makes us strive towards some kind of wholeness.

That reminds me of something Coleridge said about the necessity of opposites. If we didn't have sadness, how would we appreciate joy?

Wilson's book, Against Happiness: In Praise of Melancholy will be published this year.