This book is about how your impact can live on forever, and that’s something I think we all want.

Creating a legacy was already on my mind when, at nearly fifty years old, I sold my boutique hotel chain, Joie de Vivre. A couple of years later, I joined Airbnb as a mentor to its co-founder and CEO, Brian Chesky, and as Head of Global Hospitality and Strategy, reporting to Brian. (Yes, it’s unorthodox to mentor your boss, but given that 40 percent of Americans now report to someone younger than them, we’re likely to see more of this in the future.)

I’d never worked in a tech company before. I didn’t read or write code. I was nearly twice the age of the average Airbnb employee, and I reported to a smart guy who was twenty-one years my junior and the CEO of the company. Brian had asked me to be his mentor, but I felt like an intern.

Modern Elder is the phrase I coined to mean both mentor and intern, student and sage. Modern Elders are coaches and collaborators, appreciated for their expertise and humility. Their curiosity opens up possibilities; their wisdom distills it.

Marc Freedman, one of the wisest thought leaders and most committed students in the aging and longevity world, has been my Modern Elder. This book is his masterpiece.

Marc popped up on my radar about ten years ago, even before I had an inkling of an interest in aging, longevity, or mentorship. The first thing I noticed when we met was just how generous he was with his time and attention, his contacts, and his optimism about what I was working on. And how sincere. Marc believes down to his toes about everything he does.

As I got to know Marc better, I began to see him as a beautiful alchemy of head and heart. He has a lot in his head, no question. No matter what topic I introduced, he was my librarian. At Airbnb, I was the librarian for all my younger colleagues. But in my conversations with Marc, whether we were talking about basketball or politics or longevity, he had the facts and the contacts at his fingertips and shared both freely. He’s a mensch and a mentor—a mensch-tor, you might say. And there aren’t too many of those in this world.

And then there’s his heart. How to Live Forever is one of the most heart-centered books I’ve ever read. It’s hard to read this book without getting choked up by Marc’s superb and poignant storytelling. He has a gift for remembering and articulating details, conversations, and connections made across generations.

I’m drawn to this book, too, for its understanding of the power of intergenerational collaboration. For the first time, we’re routinely seeing five generations in the workplace at the same time. That age diversity has huge potential value. There’s growing evidence that age differences—in life experience, perspective, cultural framing, understanding of customers, even how the brain works—add up to smarter, more effective teams. And smarter, more successful organizations.

How to Live Forever is a soulful rallying cry for intergenerational collaboration like we’ve never seen before. Marc’s optimism around a new generational compact, forged together and benefitting all, is more than inspiring. It’s energizing. I finished this book brimming with optimism about our future. I hope you will, too.

If you’re my age, chances are you may live another thirty or forty years. And, if you’re anything like me, you likely want to live a life that is as rich and meaningful as it is long. If you keep your wisdom to yourself, it dies with you. But if you can lend your gifts of age to the next generation, that wisdom will never grow old.

I’m so grateful that Marc lent his wisdom to me—and to all of us—in this book. Its message will never grow old.