Health, wealth, good looks and status have astonishingly little effect on what the researchers call "subjective well-being." 
Psychologists have amassed a heap of data on what people who deem themselves happy have in common. Mood and temperament have a large genetic component. In a now famous 1996 study, University of Minnesota psychologists David Lykken and Auke Tellegen surveyed 732 pairs of identical twins and found them closely matched for adult happiness, regardless of whether they'd grown up together or apart. Such findings suggest that while we all experience ups and downs, our moods revolve around the emotional baselines or "set points" we're born with.
In his book, "Authentic Happiness" (Free Press), University of Pennsylvania psychologist Martin E.P. Seligman tells us that happiness is not about maximizing utility or managing our moods. It's about outgrowing our obsessive concern with how we feel. He says, "The time has arrived for a science that seeks to understand positive emotion, build strength and virtue, and provide guideposts for finding what Aristotle called the 'good life'."
Beyond pleasure lies what he terms "gratification," the enduring fulfillment that comes from developing one's strengths and putting them to positive use. Half of us may lack the genes for bubbly good cheer, he reasons, but no one lacks innate strengths or the capacity to nurture them.
Source: The Science of Happiness by Geoffrey Cowley (with Anne Underwood) in Newsweek, September 16, 2002