It's hard for a 42-year-old to issue retrospective advice to her "struggling" 18-year-old self when, within a decade, that teenager will be a pop sensation, married to one of the globe's most famous and handsome sportsmen. I mean, that 18-year-old's plan for world domination seems to be pretty solid, doesn't it?
Whereas most popular entertainers spend 10 years or more waiting tables, working at call centres and maintaining a spirited pretence at being an actor or singer, Victoria Beckham (for it is she we're talking about) was in the Spice Girls' line-up by the time she was 20.
So it must have been a challenge when Vogue asked its October issue cover star to pen a sympathetic missive to her younger incarnation: "Hang on in there, sweetie! You have two whole years to wait before you join the most successful girl band of the 1990s."
In fairness to Beckham, she manages some convincing sentiments about being the plump girl with acne at the back of the chorus line: "You are not the prettiest, or the thinnest, or the best at dancing at the Laine Theatre Arts college."
And she's sweet about her first meeting with rising football star Becks "in the Manchester United players' lounge" - even if she feels compelled to add, "He's not even in the first team at this stage; you are the famous one."
However, you can't help but feel wistful for all the advice left unissued. The sort of home truths no woman utters in a glossy fashion bible. Where, for instance, is the assurance that no one will ever think of Beckham as "Posh" in a post-David Cameron and Downton Abbey world?
A searingly honest type might warn their distant teen personage to never let their husband say he wears his wife's knickers, or to let him within two inches of a buxom Spanish PA. Young Victoria might also feel compelled not to give the interview to the Spanish paper that reported she'd never read a book. None of this would make such a touching letter, but it would resonate more widely with non-superstars.
Most of us make such big, comedic errors in our youth that it only behoves us to come clean about them. To share, so that others may laugh freely at our pain.
I would not get into a yellow VW Beetle with the registration number "666" and allow its young, stoned owner to drive me and two friends through a "No Entry" sign on to the wrong lane of a motorway. I would advise against taking off all my clothes in the school's sixth-form swimming pool and allowing my classmates to take incriminating shots. I would not tell my beloved mum, in a fit of hormonal rage, that she was less attractive than my aunt and it was no wonder my dad never took her out.
What you know by middle age - or should know - is that your greatest regrets aren't youthful mishaps, but the things you didn't do. I wouldn't just be advising my teenage self to master French and Spanish and the piano or guitar, I'd be bullying them to do so. And I'd urge myself to keep a diary, because my memory will be shot by 48. And why on earth didn't I buy that beach hut in Whitstable that my friend Nick was offering for 200 in 1992?
Of course the truly interesting letter is the one your teen self would write to the middle-aged proselytiser, asking, "What entitles you to be so blooming patronising?" Victoria Beckham's younger self might lament the fact that the woman who once dressed like a drag queen, now designs minimalist shift and sack dresses for dour fashionistas. Mine would say, "If you're so wise, how come your free-range children ignore you and why haven't you paid off your mortgage? P.S. Lend me 200 and you can sell that beach hut for a fortune one day."