Diane Rehm is at a crossroads in her life. Her husband, John, died in 2014 after years of living with Parkinson's disease. She plans to retire next year from her National Public Radio call-in program, The Diane Rehm Show, ending a 37-year career in radio. In September, she will turn 80.

In her latest book, On My Own, Rehm walks readers through the most recent year of her life, struggling with living alone and figuring out a new identity. Some chapters focus on particular challenges of living alone. Others are more like journal entries, guilty and angry at how her husband was unable to die on his own terms. Others are letters to a husband no longer here to hear them.

Rehm became involved with the right-to-die movement after doctors refused to help her husband. He purposefully stopped eating and drinking. It took him 10 days to die. She plans to spend part of her "retirement" working with Compassion & Choices, a nonprofit organization that works to improve patient rights and individual choice at the end of life, including access to medical aid in dying.

From her home in Washington, Rehm talked about her newfound passion in the right-to-die movement, the challenges of marriage, and a certain guest who answered his cellphone during her show.

Was it cathartic writing this book?

I started writing it the night John was dying, and I had stayed there [at Brighton Gardens Senior Facility, near Rehm's home in Washington], sleeping on two chairs. I got up at 2 in the morning, and I couldn't sleep, and I had my iPad with me, and I started writing right then. In a sense, I wanted to record what I was feeling, and I really wanted to be in that moment. It's hard to say it was cathartic, because I knew he was going to go soon. I would say I was being true to myself.

What was the biggest challenge you faced in that year? You write about your fear of being alone.

On one hand, I had already been alone for a number of years as his disease progressed, both while he was at home and then for a year and a half when he was at Brighton Gardens. But when he died, that's a different kind of aloneness, and that was what I needed to realize and come to grips with.

Your book speaks to a specific generation of women, who went from their mother's house to their husband's house. What would you like today's generation to get from reading your story?

Today's generation is very, very different. I'd like them to see how important it is for two people in a marriage to truly understand each other and have a really good sense of who the other is by learning to listen to each other. And secondly, I wanted to write that book to encourage people to talk realistically about how they want to die, and what they want from their death - do they want to go by the grace of God, because if they want that, they should say that. Say it on paper and in wills and to doctors and lawyers, to everyone.

How have you faced your fear of being alone?

Well, I have my dog, who comes with me every single day into the office. You know, it's a funny thing about little dogs: He's so beloved and so protective of me, and I talk to him a lot. And I have a wonderful group of friends that I'm in contact with daily, and I'm in the office with my wonderful producers and coworkers.

When I move away from the microphone, it won't be retirement. Retirement is not the right word. I will still continue to be involved in WAMU [the originating station of her program] as well as other organizations, like Compassion & Choices and Us Against Alzheimer's and the Parkinson's Action Network.

You've been interviewing people a long time. What's the craziest thing anyone said on your show?

It's not what someone said, it's what they did. When Tom Wolfe was on the show, he was dressed in his wonderful white suit, and in the middle of the show, his cellphone rang. And do you know what? He answered it and began talking to the person on the end of the line, "Oh, I'm on The Diane Rehm Show," and I'm saying, "Tom, Tom. . . . " That is the nuttiest thing that ever happened.

You tell a story about interviewing Fred Rogers, the Mr. Rogers of TV. He said that when he was sad, he played the piano, and he'd been playing a lot lately because his stomach hurt. You didn't ask him why his stomach hurt. He died three months later of stomach cancer. You tell this story a lot, and it clearly haunts you. Why?

I don't think I've encountered anyone like dear Mr. Rogers. I loved him so much because he taught me so much about how you treat people gently and tenderly and with honor.

Those are almost the exact words you use to describe your husband throughout the book: that he taught you so much and that he was a gentle man who treated people with respect.

[Pause.] Well, that gives me something to think about, doesn't it?

How have you changed as an interviewer?

I have learned to listen more carefully, and I've learned to probably use my intuition even more, and to not always stick to the facts and rely on what I've read. It's why I use Skype when someone is out of town. I want to look into that person's eyes and want to see how that person moves when they're in the studio. I think I've learned to be more understanding of people's frailties and more aware of where they are strong.