There are two varieties of self-reflection. One is meditative, possibly even cosy – your thoughts, a pot of tea, an armchair. For the other, you look in a mirror and regard your mortal image. From an early age, I treated birthdays like mirrors. When the day arrived, I’d step back, squint my eyes and coldly scrutinise each feature – the preparations, the celebration, my companions, the gifts – convinced that if I caught all the angles I’d see a full portrait of My Life, and be able to judge it accordingly. As in, ‘Yes, things are how they ought to be,’ or, ‘No, it’s time to make some changes.’

I know this because back before writing emails to friends became my preferred (and precarious) method of journal keeping, I carried an old-school diary wherever I went. But recently, when I opened one, and then another, expecting to read faithful remembrances of birthdays past, I discovered that for many years I made no mention of the day, and when I did, it wasn’t a description but an elaborate critique. Meanwhile, the birthdays that live in my memory as exceptional have no written record.

Take my 21st, legal drinking age in America and therefore a milestone, though it glows in my mind’s eye for reasons other than alcohol. Growing up, my birthday was a family affair. 
I was born on 5 July 1972, and my brother four years and one day later, fating us to a childhood of shared backyard parties. In my early teens, my parents began renting a cottage for several weeks each summer on an island called Vinalhaven, off the rugged coast of Maine, and 
‘the birthdays’ graduated to gorgeously messy seafood feasts: lobsters hauled from the ocean, bowls of steamed clams, corn on the cob and 
chocolate cake (two, of course).

During my second year of college, I fell headlong for W, a wry painter poet with floppy, dirty blond hair, who quickly won over my brother 
and parents; that summer, it was a given he’d 
join us in Maine for my 21st. The night of ‘the 
birthdays’, I remember looking across the dining table, bright with lobster shells and bottles of beer, marvelling over how easily W had slipped into our Bolick dynamic. We all assumed he’d stick around forever, a lovely thought those first couple of years, and then – to my surprise – less so when we finished 
university. Our parents’ generation had 
married just out of college, which I could hardly wrap my head around; there was still so much I wanted to see and do before settling down. 
We broke up, got back together, tried to make it work long distance – a torturous limbo. And then, just before I turned 24, my mother died unexpectedly from a swift, ruthless form of 
cancer. W and I were too inexperienced, and our commitment too battered, to survive my grief. My 25th birthday was our last together.

After that one-two punch to the gut I had no intention of falling in love again any time soon – I frankly didn’t think myself capable – but I did, that winter, with R, a kind, gentle editor at the magazine I’d started working for directly after my mother died. And so I spent the rest of my 20s ensconced in the familiar cocoon of coupledom, albeit with increasing ambivalence. A voice in me said I needed to learn how to be on my own, beyond the safe harbours of boyfriends and family, but the thought was so uncomfortable I couldn’t bear to listen.

Twenty eight isn’t a milestone birthday in the traditional sense, but it was certainly a major turning point in my life. Recently, I found a snapshot from that day. R and I were about to leave Boston so I could attend graduate school in New York City and, before the big move, we’d rented a cottage on Vinalhaven, just the two of us. It was that burnished hour before dusk when he took the photo: I’m standing at the edge of a field of wild flowers, hands on my hips, the ocean beyond, looking very much like someone who’s got her life figured out. Career path, check. Great relationship, check.

But if you look closely, you can see that my smile is big but not welcoming. It’s the smile of someone erecting a barrier behind which she can gather her things without being seen, shove them into a suitcase, and flee – to who knows where? She has no idea. From the diary: ‘Here on Vinalhaven I keep worrying over the matter of marriage to the point where it’s difficult to enjoy myself. Where is this relationship going if not in that direction? And is it the right direction? And how does a person know?’

Before a year was out, we were finished. It was a bad break-up, and I was in no mood to celebrate 29; I can’t find a record of the day in my diary, or in my memory. And yet a lot can happen in a year. I found an apartment with a friend in Manhattan, finished graduate school and began my freelance writing career. As the dreaded 30 approached, I marvelled that though in college I’d assumed I’d be married by now, here I was, happily – dare I say euphorically – single. When people asked what I felt crossing into my third decade, I was amazed by the truth: relief. Finally, I could release the twentysomething burden of trying to figure out my life and just be. Hello, world, here I am: me! Nothing more, nothing less. That morning, I sent an email to everyone I knew inviting them to a dive bar on the Lower East Side and stayed out drinking and talking all night.

I’m sure if I asked a scientist I’d learn that euphoria is a lot like lust: it flares up, then out. I’d expected those early years on my own to unfurl like a paper party horn – one strong blow, and a multicoloured blast of good cheer rolls out. I’d forgotten they shrink right back to their starting position. In this way I stutter-stepped into singledom, each bold advance followed by a deflated retreat.

And then I turned 32. From my diary: ‘I am moving into my own place, which is beautiful. And I’ve done it all myself. I am on my own. I am not alone. I am building a life that 
is good. And there is more good to come.’ I was right – life continued to have its ups and downs, but each passing year was better than the one that came before. During my tightly coupled 20s I’d sometimes envied the freedoms of my 
single friends, but as they disappeared into marriage and motherhood I felt lucky to be alone in my 30s, when liberty is combined with maturity, and has a lot less to do with hanging out at bars. I travelled on newspaper and magazine assignments – Amsterdam, Buenos Aires, Rome – met interesting people, my relationship status and geographical location in perpetual flux, myself the only constant.

At 35, I was a little dismayed to realise I still hadn’t married, until 
I looked in the birthday mirror and thought, ‘Wait a minute, you’ve already made a commitment – to living your life the way you want it. Maybe you don’t want to be married. Or maybe you’ll marry in 20 years. Get over it. Own your choices.’ And, 
honestly, that was that. I stopped conjuring the ghost of should-be-married-by-now and revelled in a life untethered, mistress of my own domain, solely responsible for my time and money: write all night, fly last-minute to see a friend, take squash lessons, spend a weekend reading in bed, host an elaborate dinner party for 10. Fully inhabiting my self-reliance helped me take dating less seriously, which made it more fun. Relationships breathe easier when they’re freed from a timeline.

If 30 had been a relief, 40 was a triumph. I’d made the life I wanted. That year, a dear (married) friend and I 
co-hosted a blowout: a seafood feast for 40 on the coast of Massachusetts – ‘the birthdays’ all grown up (my brother was there, with his wife and two daughters). I was newly dating a man, also a writer, and not at all concerned about where we were headed, though of course other people were. So often, expectations are carried by those around us, not ourselves, though it can be hard to tell the difference. At that point, living alone for nearly a decade had made me better at hearing, and listening, to my own voice.

By the time you read this I’ll have turned 43, the low foothills of middle age and, when I look in the birthday mirror, I like my reflection. I remain unmarried and still live alone, though, three years later, I’m still seeing the writer. When people ask if we’ll move in together, or put a ring on it, as people do, I tell them to slow down. I’ve finally come to see that single vs married is a false binary anyhow. The good life is composed of elements that transcend relationship status: creating your own security, nurturing relationships with friends and family, building a support system, 
mastering a vocation or skill. The great novelist Edith Wharton put it best when she wrote in a letter to a friend: ‘I believe I know the only known cure, which is to make one’s centre of life inside one’s self, not selfishly or excludingly, but with a kind of unassailable serenity – to decorate one’s inner house so richly that one is content there, glad to welcome anyone who wants to come and stay, but happy all the same when one is inevitably alone.’

Spinster: Making A Life Of One’s Own, by Kate Bolick, is out now (Crown Publishing Group).