A couple of years ago, after a bad academic year, I’d thought things would get better over the summer. They didn’t. I kept walking out of shops without buying what I’d gone in for, because it felt wrong to be taking up space and expecting attention. I couldn’t buy train tickets, even at the machine, because other people deserved to go first and, as soon as there was someone behind me, I gave up mid-transaction. I wasn’t eating much – food was for other people – but at the same time I was travelling and appearing at literary events and festivals, confident on stage as I’d been confident in the classroom all year. It seemed to me that my low estimation of myself off stage was correct and so I didn’t think to seek help any more than I’d seek help for believing that rain is wet.

One day in September (kids at school, students still on summer vacation, a time when work can be done from a train or hotel), I was in Paris, changing trains, really, but still with enough sense to know that a person arriving at night and leaving the next day might as well leave late the next day and give herself a day in Paris. I wasn’t sure it would work, knew myself perfectly capable of walking the streets hour after hour telling myself that any competent person would be enjoying museums and shops and cafes and what kind of privileged neurotic steals a day from her work and her family and then doesn’t even have the guts to buy a croissant, days off are wasted on me and I don’t deserve … I knew the city, a bit, from teenaged (mis)adventures, and I set off into the Marais, hungry from missed meals the day before and carrying a backpack too heavy with books. Sunlight through plane trees, the streets still quiet. Old stone, balconies, geraniums, city squares with those perfectly geometric arrangements of trees and municipal planting that we don’t do in England.

I sauntered. I passed a couple of cafes where people sat outside with newspapers, café au lait, tartines. I paused to read menus, though I knew what they’d say and I knew what I wanted, une tasse de chocolat chaud et des tartines au beurre, the breakfast offered by my friend’s mamie every morning in the French Augusts of my teens – in delightful contrast to my sugar-free, wholegrain upbringing in Manchester. There was one cafe in a colonnade, overlooking a garden across which children hurried to school, several people breakfasting alone, and several free tables. I could maybe, I thought, I might not panic if – I did. The ancestral voices were too loud for chocolate and white bread but not so loud I couldn’t order fruit and tea (you do know you could buy that down the road for tuppence ha’penny, you know you’ve just spent all that money on some leaves and hot water). I sat there, in the sun, reading and sipping, almost like a real person who was allowed to be there. I tipped the waiter almost like someone who wasn’t raised by Yorkshire folk.

I strolled on. The Picasso museum was closed, but I found it funny rather than another symptom of moral failure that I had, yet again, tried to go to a European art museum on a Monday. Shops began to open. Presents for the children, I thought. A box of patisserie – tissue paper, ribbon, smelling of French butter – that will be a nuisance on the train but a small miracle at home in Coventry after dinner tonight. I backed out of the first place I tried – too grand, not for the likes of me – but managed well enough at the second, and then, wandering into the Pletzl in the Marais, I found a Jewish bakery selling some of the cakes of the other side of my childhood, poppy seed and sour cherry. Another ribboned box. More strolling, and then a public garden glimpsed through the gap in an old wall, which turned out to be the memorial garden to the children of the ghetto. I knew about those children from researching a book I’d written and abandoned, and I sat there with their memories. New small children came to play.

I wandered on, passed again the window of a silversmith where I’d admired a bracelet earlier. It was open now and I found I could go in, try on the bracelet. (How much? On yourself, just like that, for no reason? You want your head looking at. Who do you think you are?) I walked some more and sat in another park and watched people and ate a sandwich and a rather lavish piece of cake, and then I went back and bought the bracelet because that afternoon I did briefly know who I am: a woman with a silver dragonfly on her arm, a women who can buy herself a silver dragonfly.

I don’t mean to say that shopping cures melancholy. I don’t mean that consumerism isn’t destroying the planet. I don’t mean that being privileged and sad is real suffering. Maybe I shouldn’t have bought my bracelet. Or maybe we’re allowed to find small joys, in proportion to our situations, on a burning planet with the ancestors howling in our ears.

• Sarah Moss’s new novel The Fell (Picador, £14.99) is out now. Buy a copy for £13.04 at guardianbookshop.com