Good relationships.

In fact, good relationships are significant enough that if we had to take all eighty-four years of the Harvard Study and boil it down to a single principle for living, one life investment that is supported by similar findings across a wide variety of other studies, it would be this:

Good relationships keep us healthier and happier. Period. So if you’re going to make that one choice, that single decision that could best ensure your own health and happiness, science tells us that your choice should be to cultivate warm relationships.

But money, achievement, and status all have a tendency to overtake other priorities. This, too, is a function of our ancient brains: we focus on what is most visible, and most immediate. The value of relationships is ephemeral and hard to quantify, but money can be counted.

Focus first on what’s working well. This is the easiest place to begin. Take a look at the relationships on the energizing side of your social universe and consider how you might solidify or encourage what’s great about them. Tell (and show!) those people how much you appreciate them, and why. It never hurts to double down on what’s already bringing energy and vitality into your life. These relationships are already rolling, but there are usually one or two that have slowed down and need a little push to get up and running at full tilt again. Even good relationships tend to repeat the same routines over and over. It might be time to try some new things with them.

If we accept the wisdom—and more recently the scientific evidence—that our relationships really are among our most valuable tools for sustaining health and happiness, then choosing to invest time and energy in them becomes vitally important. And an investment in our social fitness isn’t only an investment in our lives as they are now. It is an investment that will affect everything about how we live in the future.

Henry’s realization about wanting to be around people also teaches us an important lesson—not about retirement, but about work itself: the people we work with matter. It’s important to look around our workplaces and appreciate those coworkers who add value to our lives. Since work is often so shrouded in financial concerns, in stress and worry, the relationships we develop there sometimes don’t get their due. We often don’t notice how significant our work relationships really are until they’re gone.