Joan Baez has been singing her songs of protest for 60 years, her matchless soprano voice rising above trouble. She can look back on an extraordinary career that included a new interpretation of Bob Dylan songs in the 60s, and singing for Martin Luther King (with whom she became friends). The daughter of a Mexican-born physicist and a strong-minded Scottish mother, she has announced, at 78, that she is now on her last tour, performing her swansong album Whistle Down the Wind.

What moved you to record the album Whistle Down the Wind after a 10-year gap?
I felt it was time. I’m phasing out and wanted to choose something to bookend my first album. My original album has a song about a silver dagger; my last a song about a silver blade. The first was a traditional folk song – the girl lost out. In the last, which was written for me, she turns round and kills the guy – she could be part of the #MeToo movement.

You are 78 and on your last tour – where do you get your incredible stamina? What is the secret to taking such good care of yourself?
My mum lived to 100 and never had any serious diseases. My father died at 94 with all his hair and teeth. I’ve a lot to live up to… caring for myself? The most important element is the Gokhale Method, which is all about posture and based on native women who stand straight even after picking rice all day and don’t have any back problems. And meditation, even though it has always slightly bored me, is important. Plus pilates and yoga stretches. And at my age, walking is the best exercise. I have a lovely field I walk across every day for about 40 minutes.

And your voice? What does it need – rest or exercise?
Both. But what has been exhausting is reconstructing every song I ever wanted to do in a low, limited range. I love how Whistle Down the Wind came out, but my voice will continue to deteriorate no matter how hard I try.

So you don’t plan to arrive at the Leonard Cohen growling stage?
Well, they’re guys and somehow get away with it better...

I loved your anti-Trump song Nasty Man on YouTube, a viral hit, in which your sympathetic performance is in delicious contrast to your subject...
Have you read Trump on the Couch? It’s a wonderful book, but its main message is that Trump is incapable of change – no compromises, no backing off, my button is bigger than your button.

So depressing… are you an optimist or pessimist?
When I was 15, I thought of myself as a realist. But now I have to remain in denial for a good portion of the time because otherwise I’d go crazy. You have to measure what you do in little victories that reintroduce compassion and empathy. We won’t have social change until people are capable of taking risks again.

You’ve been an activist all your life. But can a song change anything?
Songs change a lot. Music lifts the spirits, crosses boundaries and can move people to do things they would not otherwise have done.

Do you still define memory as you did in your song about your affair with Bob Dylan as “diamonds and rust”?
That song went down to the bottom of my soul… I don’t know where its words came from.

Is it inevitable your name will always be remembered alongside Dylan’s?
Well, what happened recently was that I painted some pictures of him, and I put his music on, and any stuff that was getting in the way, any jealousies, any resentments, completely vanished. And maybe it was to do with this time in my life, and maybe it was to do with realising that you can hold grudges for only so long. And that it is stupid to hold grudges. The Buddhist training is that you forgive.

And on top of that I felt: oh my God, your name is going to be attached to somebody for the rest of your life… and this is an honour because of what that guy created. And you know, he’s not socially gifted, but that doesn’t matter. He can take an artist’s liberties as far as I am concerned.

In every interview, you are defined through famous men: Dylan, Steve Jobs, Martin Luther King. Which woman has most influenced you?
Emma González, representative of the youth movement. We have to depend on the young – they unite about climate change. We adults don’t know how to deal with it. That little movement has the most potential of anything we’ve seen in the US in the past 40 years. The other woman who influenced me was my mother. She was so funny. When I asked what she wanted for her 100th birthday, she said: “To drop dead!” A week after, she did. I was influenced by her connection with nature, living in the woods. My home is in a very civilised wood in California.

Do you mind getting older?
About two years ago I thought, oh my God, I’m going to be 80, and so I went about the house saying: “I’m going to be 80” for about a month. It doesn’t bother me now. My other female heroes include Meryl Streep, who campaigns to stop women rearranging their faces through surgery. My goal is to embrace the wrinkles.

Speaking of homes, I’ve heard you’re a disciple of Japanese decluttering queen Marie Kondo?
I was messy when I was little, but later realised you need to keep things orderly because your house is your brain: everything in it is a reflection of what is going on inside of you.

Your son Gabriel has been with you on tour as percussionist. Do you feel this makes up for the time you missed with him when he was little?
He will finish the tour with me. It has been more than any mother could have dreamed, because most mums don’t get to hang out with their sons once their sons marry.

How do you plan to spend your time when no longer performing?
I will paint. And I love to dance – maybe I’ll take classes in Latin dance.

You won’t stop singing?
The more my voice deteriorates, the less happy I am with it. Humming around the house it’s all flat and cockeyed and I think [laughs] maybe I’ll just talk to myself instead.

• Joan Baez’s Fare Thee Well tour is at the Bridgewater Hall, Manchester, 25 Feb; Royal Concert Hall, Glasgow 26 Feb; and London Palladium 28 Feb, 1 March