And if you're a shy introvert, putting yourself in uncomfortable social environments will shave time from your life. I'm glad I learned to keep my social interactions more personal. They fuel me when they're one on one or a groups of three. Going to large group events in my 20s was a major source of anxiety, but now I just avoid them (not that they happen so much when you get older anyway).
It makes sense that things that make us happy can improve the way our bodies work because it's been obvious for a while that things that cause stress contribute to bodily wear and tear. But it's worthwhile to find evidence because that's how we do science, so I'm happy it's being considered and studied.