The Portuguese artist Paula Rego once said: “Work is the most important thing in life.” I agree with her. Work defines who we are in the world. It gives us purpose and direction. It is how we manifest ourselves in the sphere of public functionality. Without it, we might come to feel like less effective citizens, taking up physical space with less power to define the shape of our exteriority. I think that what Rego was implying was not that family or the other elements of our lives are not important, but that those things cannot exist in balance without the fact of work. Every day she would go to her studio and immerse herself in her paintings and prints, the nucleus of her existence. When it was finished, she would come out fulfilled, capable of full relaxation and communication with others. I am describing here something akin to my own optimum experience of work and transposing it on to Rego, because the satisfaction of and need for creative industriousness in the artist’s life is presumably common across disciplines. There is no bliss quite like the end of a successful writing day, when I have achieved a good word count, when I have travelled through the words arriving on the page and lost myself in it. Achievement, according to psychologists, is an essential human need, next to food and shelter. Writing regularly and often is crucial to my mental health and, especially while writing a novel, I like to work as consistently as possible – days off make me nervous.

I realise that there are parents out there who savour school holidays, who see them as a time of relief, a break from routine, a chance to spend quality time with the children. But it has to be said that the school holidays go on for an inordinate amount of time. Families do not need to spend that much time together. They need their dispersings and distances in order to come back to one another ventilated of small irritations and tetchy dynamics.

At the same time as having a child about to start secondary school, and one about to leave for university, I recently spent a year moving my elderly mother to a retirement flat closer to where I lived, so that I would no longer have to worry about her falling down the stairs 16 miles away, or being broken into in the middle of the night with only the stick that she kept under her pillow to defend herself with.

Whereas previously I had maintained a strict rule of no family admin in the creative space, now I found myself reading an extracurricular sports booklet in place of morning poetry, for instance, or highlighting lists of stationery equipment or trawling through deadening parental emails, alongside taking my newly closer mother to closer dental and doctor’s appointments. I was not alone in all this – I had a partner and siblings on hand – but out of a zodiacal need for thoroughness and efficiency, I had unintentionally taken on the role of project manager, so I was laden with distraction, and there is maybe a whole other essay here about gender differences in relation to thoroughness and how easily any discord arising therefrom is put down to maternal martyrdom. Ultimately, I could feel a crack beginning to form in the hard wall of distinction I had built between writer and mother.

After weeks of dealing with the scramble of tasks involved in helping my mother settle in, helping the children towards their new chapters, and in the midst of these trying to write, I was on the verge of full-scale, agonising burnout, gasping for retreat and seclusion. There was simply too much in my life, and the part that most belonged to me was shrinking.

***

My friend told me about it – the sandwich. We were sitting at her kitchen table and I was relating to her all the above. “Oh yeah, the mid-life sandwich,” she said in quick recognition. I hadn’t realised there was a name for it, that stage between the ages of 40 and 59 when a person can become saddled with caring for aged parents and raising children at the same time. First coined in 1981 by social workers as the “sandwich generation”, in the UK about 3% of people fall into this category, but the numbers are growing: “Not only is sandwich care becoming a more common phenomenon,” says an Office for National Statistics report, “but carers are finding themselves caught in the sandwich for longer”. This is to do with an ageing population, the fact that children are staying at home longer, and that many people are choosing to have children later. It was comforting to learn that the situation I was struggling with was a certified, widely experienced predicament.

An important element of the mid-life sandwich, which affects its taste, texture and digestion, is of course the filling. For a woman, flattened within the doughy weight of the two slices of bread is likely a substance in transition, undergoing the momentous internal shift posed by menopause. Her body is changing. Her oestrogen is falling. There may be waves of heat, spreading across her at intervals. There may be heat that comes and then turns cold so that she is left soaked and shivering. Anxiety and brain fog, so that her thoughts become hazy and unclear. Interrupted sleep, low mood, low libido, clumsiness, sex pain. I have seen women in this transition looking out at the world with meekness where they were once bold. I have sensed their reduction, their growing habit of self-deprecation and apology, while men of a similar certain age may well flourish in the opposite direction, becoming distinguished and silver-foxy, weather-beaten and “experienced”. The reason why Sex and the City was such a successful show is because of how flamboyantly it rejects society’s desire to relegate maturing women to unbeauteous and sedate invisibility.

So at a time when a woman needs more than ever to take care of herself, she is pulled in two directions, taking care of others. Meanwhile the world around her flaunts its long-prized pictures of what she fails to embody. Women need a kinder, safer society in which to age. Our bodies, our very eyes, are stolen from us by the culture as a form of control, and by the time of the midlife turn, beauty has become a prison, targeted by Botox salesmen, retinol, vitamin C serums, eye creams, liquid collagen, chemical peels, hyaluronic acid injections, hair dye, dermal fillers, laser skin resurfacing, psychotherapy and much, much more. Imagine if throughout our lives we had been told by the world at large that we are beautiful in our many forms. Imagine if the icons and idols paraded before us looked more pervasively true and representative. How boldly we might walk on to our later time. How we might strut and hold up our heads, full of everything we have seen and come to know, and how much more lovingly we might meet ourselves in the mirror, watching with fascination instead of terror the way our faces change and physically take on that knowledge, which is the beginning of wisdom. These faces, these bodies are the only ones we have, and there is only so much you can do to change without breaking them. The most useful and practical tool a woman can have as she ages is self-worth.

The sandwich, then, is quite a mouthful – not a snack, more a large-portion, high-calorie main course. Beauty fascism aside, how should we respond to the multiple demands made on our time and energy while preserving our own wellbeing? Is this the time that we surrender ourselves, and give in to the new forms our lives are drawing us to fill, or should we attempt to hold to the shore that seems to be slipping away, leaving a place there to return to when we are free again and our labours are done? I realise increasingly that if you try to fight the organic, logical course of your journey through life rather than flow in its direction, you are at risk of becoming either crazy or lost, or at least, extremely tired.

I have always been a fast eater. When I was a child I used to shock my family with how quickly I could shovel through a meal without appearing to, and I am the same now. But this sandwich thing takes slower consumption. I am learning to pause and observe, to hold it in my hands and look at it, turning it around, noticing the texture, the taste, instead of charging through until it is all gone. Alice Walker wrote in Now Is the Time to Open Your Heart, “You would not drive a car looking out the side window, would you? Yet that is what it has come to for many human beings; they are driving their lives forward while watching what is happening along the road or even in the rearview mirror.” She is talking about paying attention. About living in the present moment, and that connection, that presence, is where our strength is, the fuel that takes us safely onwards.

I still agree with Rego that work is the most important thing in life, even though I did not achieve what I had wanted to achieve that year at my writing desk. My attitude towards the idea of achievement is shifting. Work is the most important thing, but there are times when the other components surrounding it take precedence, for just a little while, or for longer. Those other components are the great wheel of our existence turning, the image of who we are and how we live, and it is necessary at some juncture to stand back and look at them, to stop what we are doing, put down our tools, go out into the open air and witness the reality of humanity. An old woman, for example, in a new place far from home, and the slow, necessary assembling of what is familiar to her so that she can go on: her pictures on the walls, a clock by the kitchen, a drawer for her plethora of scarves. Or the closing summer of a daughter’s childhood before she leaves into the world, the anticipation and innocence in her face, and the way her brother gazes at her in their playful, easy secrecy, where they can both be completely themselves. I’m glad I didn’t miss these images, that I still have them to remember. Pausing to look at them, slowing my eating, has taught me to occupy a kinder, less punitive, less regimented, looser space, which is an achievement of another kind. It is not always possible to do one’s work, and when it is not, it does not have to mean that you have failed.

• Extracted from I Want to Talk to You, published by Chatto & Windus on 6 February. To support the Guardian and the Observer order your copy at guardianbookshop.com. Delivery charges may apply.