Harvard psychology researcher Daniel Gilbert in PBS’ This Emotional Life: Rethinking Happiness (emphasis mine):
Is there a secret to happiness? Well yes, but it isn’t very much of a secret. Scientific research suggests that a lot of things matter: money, health, work, but that one thing matters a lot.
And that thing is social relationships. We’re one of the most social animals on our planet. We need each other for just about everything. So it isn’t very surprising that nature’s designed us to experience happiness when we’re connected to others.
I suspect that the health of our social relationships is going to wind up being as important as what we eat, how much we exercise, etc (sleep, stress, nature, and so on).
More importantly, this is probably going to wind up being less about us as individuals and more about how our culture is at cross-purposes with our inherent needs. Stay tuned!