Fascinating stuff published in The Atlantic with the title What Makes Us Happy?.
It's a compelling story, and an entertaining read.
In the 1930's, physician Arlie Bock at Harvard University designed a longitudinal study, initially sponsored by department-store magnate W. T. Grant, to discern the "combination of sentiments and physiological factors which in toto is commonly interpreted as successful living.”
They chose 268 male students and examined them from every angle. Brain waves, blood chemistry, physical characteristics, and more, were measured. They then tracked them throughout their lives.
Over decades, Dr. George Vaillant has observed and chronicled the study, which continues today with the survivors, all in their 80's. By the time the subjects were in their 50's, he had "identified seven major factors that predict healthy aging, both physically and psychologically. Employing mature adaptations [to the vicissitudes of life] was one. In simple words, rolling with the punches.
The others were education, stable marriage, not smoking, not abusing alcohol, some exercise, and healthy weight."
He found childhood temperament, social ease in early adulthood, and cholesterol levels in old age to be among factors that didn't matter much.
On the other hand, depression in mid-life was predictive of early death, optimists were healthier than pessimists, healthy relationships were very positive for late-life adjustments.
There's much more here. The personal stories are riveting.