My parents were teachers. My mother was also a painter. My dad taught languages and directed school plays at a boys boarding school in rural Massachusetts. He put me in a play when I was 6. It was magic—the boys treated me like their mascot, and I got to stay up late with my father for rehearsals and shows. That planted the seed.

I learned the most about the art of acting from Katharine Hepburn. But, as far as what the profession is like, it was Robert Redford. When we were doing The Great Gatsby, he asked me if I was having a good time. It was my first break in a great big movie, and I was absolutely over the moon. I told him so, and he said, “That’s great. Enjoy it. Just don’t ever think it’s about you.” It was a sobering thought. Because I thought my success was about me. But it’s a transactional affection that show business gives you. You’re making a mistake if you think your show business success is because you deserve it.

My biggest piece of luck was meeting my wife, Lynn. It was a blind date. We’re both very suggestible. Somebody told us that we should like each other, and we obeyed.

I think Lynn’s and my theory of parenting was to try to be the best people we could, and let our children see it. They see who you are and learn from that far more than anything you might try to teach them.

What I worry about most is climate disruption. As a kid, I spent summers by the ocean. It was right after World War II, and there were plenty of fish in the sea—that is no longer true. It’s one of the reasons I became involved in [the oceans conservation group] Oceana. I think there’s general clarity about what the problem is and what is causing it. But we’re at a stage where we’re asking, “Please, can’t we just burn a little more? Can’t we just lay waste a little more? And then we can be saved?” No. Now’s the time to get on the bike. Turn down the thermostat. Ask yourself, like they did in World War II, “Is this trip really necessary?” every time you get into the car. Don’t hide under the bed.

My mother and my father handled getting old in completely different ways. My father gracefully let things go. He just didn’t ski anymore, didn’t play tennis anymore. He didn’t declare he wasn’t going to do those things; he just let them go. And my mother never stopped painting as long as she lived. I thought they were beautiful solutions. I’m trying to do both!

When the possibility to return came up, I thought, Haven’t I done this already? But then I thought about what it would feel like to turn on the TV and see other people doing the show. They’ve organized production so it’s not long, arduous hours like the ones I used to do. So now I’m like a jogger who never gives up jogging; he just doesn’t jog as far. —As told to Allison Glock