Marching toward middle age is sequence of older-than moments, when you realise that you’ve passed some famous age that seemed impossibly distant as a child. First you pass the prodigies: Older than William Pitt the Younger when he became prime minister, older than Donna Tartt when she published “The Secret History,” older than Alexander the Great when he conquered Persia. Then come the athletes: When you reach your later 30s, you realise that if you had actually become a baseball star, you would now be Kirk Gibson gimping to the plate, an old man in baseball years.

This year, at 41, I picked up “A Child’s Christmas in Wales,” the great exercise in Yuletide nostalgia, which I’ve always read in an edition with terrific Trina Schart Hyman illustrations to accompany Dylan Thomas’ poetic prose. The first of those illustrations depict the book the way it reads — as an old man’s reminiscences, delivered to a grandson in the mythopoetic style: “Years and years and years ago, when I was a boy, when there were wolves in Wales … it snowed and it snowed.”

But this year, I realised that I’m now older than Thomas was when he wrote “A Child’s Christmas,” just before his untimely death at the age of 39.

The kind of nostalgia the Welsh poet summoned in his little book is likely to be uniquely powerful this year. For many people, the experience of Christmas is always measured against a memory palace handed down from childhood — different scenes from different years piled together in a vision of what the holiday should be, compared to which the exhausting grown-up reality usually falls short. In 2020 that falling-short may feel particularly painful, because separation and isolation shadow so many Christmases this year.