The Harvard Study of Adult Development is one excellent source of information on this topic.
Since the 1930s, researchers have studied more than 800 men and women, following them from adolescence into old age.
The research has shown that one of the most important factors in achieving a long and happy life is maintaining strong social relationships. Spending quality time with loved ones, belonging to clubs and societies, and being an active participant in the local community is, for many people, an important factor in achieving happiness and longevity.
Surprisingly it seems to be a more accurate predictor of this than the longevity of your parents, the quality of your childhood or the number of stressful events in your life.
So make time for your family, friends, colleagues and community, knowing you will be enhancing the quality of your own life and (hopefully) of theirs.