I heard that Joni Mitchel had appeared and performed at the Newport Folk Festival just as I was about to do an item on the radio. I mentioned it but it was hard to absorb. Hadn't she been very unwell? Hadn't we once feared we'd lost her?

The photos I saw immediately after did little to assuage me. She was seated, seemed frail. But then the reaction started: the joy, the love, the outpouring of emotion. "You have to watch this," people said. I prepared a room. I closed the door.

If you haven't watched it yet I'd better warn you: You will be disassembled and remade. All of life will flash before you. You will sing along with Both Sides Now as if it contains the distilled wisdom of our entire human history, which it may.

Part of my initial discomfort was not wanting to see one of the brightest lights of a golden generation in anyway diminished. It's what we feel and fear for anyone we love. But what will lift you is the strength and that flash of spark that is still there. It is, trust me, life-affirming.

The tension before she sings is unbearable. It is not helped by the vision of singer Wynonna Judd over her shoulder, barely keeping it together and producing a make-up mirror to check her eyes at one point. Beside Joni, Brandi Carlile, thankfully, exudes calm and gentle support.

At last, Joni sings: "Ice cream castles in the air." The world stops spinning. It is a mesmeric performance, you hang on every word. Time has only enhanced and deepened the song's meaning. By the time she sings "Well something's lost, but something's gained, in living everyday" you are broken.

Joni, now 78, wrote that song on a plane having been reading Saul Bellow's Henderson the Rain King. In the book it mentions looking down on the clouds, also from a plane, so she grabbed the opportunity to do likewise. The song came immediately.

That was 1966. Thereafter life took Joni, a Canadian, to LA, and the wonderfully creative scene based around Laurel Canyon. This is a scene long since eulogised in books and films where like-minded, talented people gathered to hang out, flirt and write songs.

It helped that those people included Joni, Neil Young, David Crosby, Stephen Stills, The Mama's and the Papa's, Linda Ronstadt and various Eagles. Famously Mama's Cass's house was the centre of most of the action and it was here that one night Mama suggested that the voices of Crosby, Stills and Nash would go well together.

This was, without question, the time to be alive. As the Sixties drew to a close, humans were landing on the Moon and the young and beautiful of America were making their way to Woodstock. It was a time when everything felt possible: world peace, sexual liberation, the freedom to be who and whatever you wanted. It was a time of peak optimism.

The film of that festival went around the world just as Joni's Newport appearance has. It seared itself into the minds of young people everywhere and with-it Joni's song, Woodstock: "We are stardust, we are golden, we are billion-year-old carbon, and we've got to get ourselves, back to the garden."

The garden was Eden, and for many at that time, that was where they hoped they could take us. It wasn't to be, of course, clouds got in the way, but the sentiment, the optimism, the purity are as wonderful now as then.

Joni's career after that was stellar of course, Blue remains a pivotal album and that moment on Bob Dylan's Rolling Thunder Review where she joins him in the dressing room to play a song is godlike. Dylan is meeting an equal, and you can tell that doesn't happen often in Bob's world.

Mitchell was turning 23 when she wrote Both Sides. Paul McCartney was a few days shy of 23 when he wrote Yesterday. Brian Wilson was 23 when he wrote God Only Knows. Dylan was turning 24 when he wrote Like a Rolling Stone. You have to wonder what was in the water. Wisdom perhaps?

You can't help looking at Joni's performance without thinking that that golden age is moving away from us, growing more distant, more dim. We didn't get back to the garden, but as she says, and it's worth repeating: "Something's Lost and something's gained, in living every day." Bless you, Joni.