When I was six months pregnant and trying to work a short, feathery crop, a trolley wallah in a supermarket car park called me “son”. That was the moment when I should have realised short hair wasn't for me. True, I was wearing trainers and combat trousers at the time (it was 1998), but, accessorised with a huge and indisputable badge of womanhood, I had imagined I could still pass for female, if not exactly foxy. I was wrong.

Undeterred, roughly every five years I get the unshakable urge to have short hair - and this intermittent itch had to be scratched again a couple of months ago. This time, there was none of my usual agonising about the style or whether my ears would be cold.

There was only one haircut in town: the Aggy, given cult status by the model Agyness Deyn and worn subsequently by the pulchritudinous Polish model Anja Rubik, the Girls Aloud babe Sarah Harding and the gorgeous celebrity offspring Kimberly Stewart - all in their twenties - and by the naughty cutie Pixie Geldof, 17. Perfect, then, for a pale, 38-year-old mother of two.

The Aggy hair exemplifies my short-hair ideals: cute, cool, relaxed, ruffleable and funky. What's more, a short cut can set you apart from the wannabe Wags, with their long, ironed hair. What I chose to ignore, however, was the fact that by the time people like me think about copying a celebrity look, its moment in the fashion limelight has passed. Even Aggy has moved on (see below). When it really is the only look in the big city, it's hot; by the time it is the only haircut in towns up and down the land, it has had it. The style death knell chimes its demise as soon as the first person copies it; that was the way with the Kate Moss fringe and the David Beckham faux-hawk.

Yet still I was possessed; I had to have an Aggy. Unfortunately, once I did, I looked hideous. Androgynous, yes, but not in a good, sexy, gender-bending-hottie-in-a-tux way - more in a freak-of-nature way. I'd been hoping more for Aphrodite than hermaphrodite. I didn't go for the full boy-length, platinum Aggy, but for a longer-on-top version, without the bleach. In other words, brunette. Reality soon started to bite: the haircut had not transformed me into an It model; I was still just me, with hair that was most likely too thin for this cut.

Edgy celebrity haircuts are simply not for civilians. The Rachel worked for everyone in the 1990s because it was long, American and family-entertainment. Extreme crops in esoteric shapes are only for the few - to carry them off, you need not only shoulder bags of attitude, but the clubbing-on-a-Tuesday lifestyle, the right clothes 24/7 and, preferably, icon status.

The hairdresser India Miller agrees. “On rounder women, or those without defined features, the cut can look too boyish,” she says. “Agyness's face and the bleach are what make the statement; it's a great package. Without the colour, it would look really dull.” A sobering word, “dull”. One that could explain why, with my Aggy cut, I have become invisible to men. I wouldn't be eyed up if I shimmied past a stag party in Rome.

Three months on, I'm still growing out my model-hair mistake - and it still looks grim. On the positive side, it does mean that I am doing my bit to protect Claire's Accessories from the credit crunch, buying enough bands and clips on a weekly basis to delight a class of six-year-old girls for a year. And I have learnt my lesson. Finally.

No more supertrendy, celebrity-inspired, short hair for me. Well, unless, perhaps, Carla Bruni-Sarkozy cuts hers...

OTHER TRENDS WE ALL NEED TO KISS GOODBYE

Orange It is not the only fruit, and it's definitely not the only nail and lipstick colour - though it has certainly felt that way recently. We loved orange for its bright, neon optimism, but it's time to move on. Next!

String headbands They started out as a hippie-centric homage to free love, beloved by the festival elite. But we need to face facts: it never had quite the same effect when nipping into M&S. We call time.

The Amy kohl-up Don't get us wrong, it's not that smoky eyes are out. As if they could be, with all the Left Bank chic in fashion this summer - where would Bardot et al have been without it? It's just that the overly kohled, looks-as-if-you-applied-it-with-DTs effect has had its day. It's not even worth sending to rehab. No, no, no.

GET IN EARLY

BLACK AND GOLD That Sam Sparro chart-topper seems to be rubbing off on the beauty mood. Black lips are everywhere for autumn, from Mac to Lancôme. It's a little bit goth, a little bit rock'n'roll and a lot less scary than it sounds. Gold, too, is proving to be a real winner. It's covering not only eyelids, but nails at Chanel, where it is truly medal-worthy.

Times recommends

• Live chat: Thrifty ways to update your winter wardrobe
• Is anybody out there really listening?
• Nutrition Q&A: Will eating late make me fat?