Georgiana died in 1806, yet her story has always felt modern to me. Her tortured relationship with food and struggles with addiction are problems that affect millions of young girls and women today. In recent British studies, between 20% and 24% of teenage girls admit to being unhappy, with issues surrounding weight and body image often cited. In one sense, it’s a relief to know that we didn’t invent a new set of dysfunctions for the 21st century. Equally, however, it’s depressing to realise that as mothers we seem to be no better at bringing up our daughters than our forebears.

When I had children of my own, I swore that I would never be like Lady Spencer, Georgiana’s mother, who wilfully ignored every warning sign of her child’s unhappiness. Her love had been the kind that damages its recipient. I, on the other hand, was going to be a positive role model, providing abundant wisdom and support. It came as a shock to discover that babies are more interested in burping and slurping than discussions on the meaning of life.

I had five children in five years, four girls and a boy. Many women would have coped better. Children have distinct needs when they’re little. They need their mothers to be present in mind as well as body, to know when to be proactive and when to stand back, and, above all else, to be their guardian and comfort. What I gave them, mostly, was guilt. Not a day went by in the early years when I didn’t feel weighed down by my own inadequacy. I felt ashamed for being so tired, for being bored, and especially for being preoccupied with my writing. I was impatient and disorganised, prone to forgetting the most basic requirements, such as warm coats and doctors’ appointments. “You’re juggling lots of balls,” a paediatrician once said in an attempt to make light of the fact I had lost track of the children’s vaccinations. “You can drop a few as long you keep the glass ones in the air.” It felt reassuring. Then I dropped some of the glass ones, too.

No child broke, but some bear the literal scars of childhood. If there are any good advice books for mothers who screw up royally, I haven’t found them. Real honesty about motherhood, not the fake I’m-so-bad-it’s-funny kind, is in short supply. It could be a holdover from all the guilt we feel. Or perhaps women are put off by the public vitriol that usually follows an honest confession. The novelist Rachel Cusk once observed that a woman who tries to tell the truth about motherhood “can find herself disowned in the very act of invoking the deepest roots of shared experience”.

My children have become tweens and adolescents; and are still burping while I’m still reassessing my priorities. Only, now, they are self-conscious actors in their own dramas rather than participants in mine. Their growing independence is like another living entity in the house; it arrived one day and made itself comfortable in my favourite chair. Ignoring its presence is not an option.

Two years ago, Cusk wrote an essay about the reality of bringing up teenage girls. Friends had warned her that adolescence is like a bad fairy: it will kidnap your child and put a monster in her place. However, she saw something different. Of adolescent anger, the bane and pain of so many mothers, she asked: is it a natural teenage reaction against being forced to conform to someone else’s version of themselves? “I wonder how much of what we call conflict is in fact our own deserved punishment for telling the story wrong, for twisting it with our own vanity or wishful thinking, for failing to honour the truth.”

Cusk’s take on the inherent guilt that comes with motherhood struck a chord for me. I think of the special punishment reserved for mothers and the message embedded in Louis MacNeice’s poem The Sunlight on the Garden as it runs through my head.

The sunlight on the garden
Hardens and grows cold,
We cannot cage the minute
Within its nets of gold,
When all is told
We cannot beg for pardon

I think most mothers, including myself, are silently screaming for pardon, but it’s either too soon or too late to make any difference. I find that to be the mother of a teenage daughter is to be thrust into a strange assortment of roles that have only one thing in common — a lack of control in life’s proceedings. Once we could make things happen with just a look. Now we say our piece and hope that our words don’t dissolve on impact. Love is strong but not omnipotent. There are large forces at play, from the hidden power of genes to the opinions of her new best friend. We can’t manufacture a happy daughter any more than we can grow a musical genius. Though, Lord knows, mothers can nip potential in the bud or, like Lady Spencer, drip poison into a fragile heart.

The theologian Reinhold Niebuhr wrote what is arguably the most famous prayer of the 20th century: “God grant me the serenity to accept the things I cannot change, courage to change the things I can, and wisdom to know the difference.” Applied to mothers, it’s a call to pick your battles, stay true and be educated. The last doesn’t require a university degree, it simply means knowing what is eternal to the human condition. We also have to be vigilant for our daughters in the present, while simultaneously preparing them for the future.

The emotional pain of adolescence is one such eternal. The term only came into use during the 15th century, but its existence prefigures civilisation by about 300,000 years. The first Homo sapiens went through a form of adolescence, as did their doomed cousins the Neanderthals. The ancient Greeks and Romans recognised there was a stage of life between childhood and maturity, even if they had no precise word for it. In physical terms, during adolescence the part of the brain known as the amygdala — which generates fear and anxiety — matures faster than the prefrontal cortex, the home of reasoning and self-control. Other than prescription medication, there is nothing in a mother’s repertoire of tricks that can force the process to speed up or go more smoothly. But eventually everything evens out, in the same way that noses, mouths and chins grow into a face.

It’s often said that there are only a handful of plotlines in literature. We could say the same for growing up. Teenage reactions to adolescence span a narrow spectrum of predictability. Our daughters either become rebels or conformists. They project their anxiety outwards, or turn it inwards. It will be a short phase or a long one. Or something in between. The lesson of Georgiana’s life is that most behaviours have deep roots. She had weight issues; so did her ancient Egyptian sisters. Egyptian tomb paintings have plenty of images of tubby men, but you won’t a find a single painting of a fat woman.

And just because it can be shown that modernity didn’t invent teenage girls or their many issues, it doesn’t follow that the pressures affecting them are no different from those in the past. Anyone born after 1995, which is every adolescent girl today, has grown up with only one reality — of life as defined by the smartphone. The impact of that change is only beginning to be understood. In a nutshell, researchers say it’s been disastrous: 24-hour connectivity has made teen girls more sensitive, more self-absorbed, more extreme and yet also less active, less happy, less confident and less sociable than they were 15 years ago.

Self-harm was a niche syndrome in the 20th century. In the 21st, it is a mode of expression for an entire generation of girls. Self-harm among teenage girls reported to GPs in the UK increased by 68% between 2011 and 2014. In the era of constant visual bombardment, “body image” has taken on a whole new meaning. A study of hashtags on Instagram conducted by the Seattle Children’s Research Institute found that #selfharm or variants of the tag had increased from 1.7m mentions in 2014 to 2.4m in 2015. Girls are living through their screens and it is crippling them. The suicide rate in America for girls is at an all-time high — and that was before the release of Netflix’s slick teen-pain-fest 13 Reasons Why. The real power of social media is its uncanny ability to disempower its users.

With so much to worry about in the present, we could be forgiven for not wanting to focus too hard on what might happen to our daughters in the future. Actually, I think this is where we have the greatest opportunity to make a difference. The truth is, despite the myriad pressures bearing down on girls today, they are vastly outperforming boys in secondary school and university. A 2015 study by the OECD revealed that 15-year-old boys are 50% more likely than girls to fail to achieve basic proficiency in reading, mathematics and science. Nor are they catching up in later years: Ucas says 30,000 more women than men started degree courses this autumn.

We have to prepare our daughters for a world where female approval — not male — will be the ultimate arbiter of success. That won’t make it easier for them. Which is why we must ensure that our daughters don’t grow up rudderless inside, like the Georgianas of this world. Becoming a success in life is a doddle compared with the challenges of becoming a woman. As for becoming a “successful woman”, the idea itself is fraught with internal contradictions — the biggest being motherhood versus a career. It’s not possible to be simultaneously in the office and at a school concert. A choice must be made and the consequences confronted. That’s a hard fact. We must fight for better salaries and conditions, but we shouldn’t look down on those who make different choices. The routes that take women to or away from careers and families are subjective and unique. I have come to believe that the criteria for judging female success are a misogynist fantasy wrapped inside a layer of fake language about women’s empowerment. The phrase “having it all” ought to be designated as a lethal weapon; or at the very least as “hate speech”, since it makes so many women feel bad about themselves.

There are days when my adolescent daughters come down for breakfast and I’m on tenterhooks as to what the weather will be. Will we have #sunlightonthegarden or a #coldandfrostymorning? The question will play itself out several more times before the day is over. I know there will be many moments like this and much else besides until adulthood beckons. I may drop a few more glass balls along the way. I may not recognise myself or my daughters by the end. Yet I believe in the final vision offered by MacNeice’s poem:

But glad to have sat under
Thunder and rain with you,
And grateful too
For sunlight on the garden.