"Autumn days when the grass is jewelled, and there's silk inside a chestnut shell..."

A walk home from work on Wednesday this week, a walk through the alley overhung by trees. I watched my feet move, dappled with light, sun-coins scattered over fans of bone that flexed and flashed, then flexed again. Then a breeze, and a drift of leaves - and the sudden shock of the falling colours, all yellows and bronzes and reds. Who stole the greens overnight, left changelings rusting in their place? Who took the softness, left parchment-paper sheaves?

I am a watcher, a notice, by nature. I see when the stars begin to hang colder, hang clearer. I notice, every year, the first bluebells chiming quietly in the garden. I see the first breath of frost in the grass. I watch the seasonal clock tick steady, even, through each neat quarter. And so I don't quite know how it happened, this year. How Summer faltered right beneath my nose. How brassy Autumn saw her chance and leapt.

How I worried about turning thirty. About leaving the word girl behind like a clue for someone younger, like dinosaur bones laid down in the dirt, the ghost of who I was preserved under fathoms of fragments and dirt. How I worried that I had spent the best of my days, my twenties, in one wild spree, that all that lay ahead was wistfulness, and thickening hips, and a hairshirt of nostalgia and fond memories.

The truth is: the only hurt of "older" is the seasons turn faster. And each one is sweeter and harder to part with than the last.

The truth is: the only thing I lost in my thirties was my heart.

A reminder to myself: Attend to the moments. The moments are important. They keep the stars, and the Poles, apart.

And so I write it, I set it here. I cast for moments, and I catch them: a wriggle of glitters, like fish in a net; a line of lights in a softly glowing string.

I realise now that the moments are the bones. The heart's-blood, the breath. The moments are the molecules and the moments are the cells. The carbon and the stars. The real, secret shape of every living thing.