I turn 27 tomorrow, when I will finally become a grown-up – according to my fellow millennials, at least.
It is the official age at which twenty-somethings now see themselves as "proper adults", a survey found this week – news that will no doubt have older generations, who were mostly married with children and a mortgage by that age, wringing their hands.
The goalposts of adulthood have shifted, however: since 2000, the number of homeowners under 35 has halved, while the average age of first-time marriage is now 34 for women and 36 for men.
All this would make my imminent birthday rather daunting, if it wasn't for the fact that I already feel like an adult. Unlike many of my peers, I've felt this way for the past few years. I'm by no means married with children, yet I have faced enough failures, successes and challenges to force me into some sort of maturity.
For Generation Y, being an adult does not necessarily mean ticking off traditional "life goals", like planning your career, settling down with a long-term partner or buying a property. Nor does it entail vowing never to step foot in a club again.
In 2017, the markers of adulthood are no longer what they used to be. For millennials, becoming a grown-up can be as simple as learning to bleed a radiator and coping with a crisis alone.
These are the signs you're really a grown-up:
You've had a break up
Nothing forces you to grow up more than ending a serious relationship, especially when it is done amicably. I'm now on break-up number two, and the pain of losing someone is no easier than it was when I was 20.
Still, I maintain that it is the best way to learn how to rely on yourself. As "millennial love expert" Samantha Burns says, a break up can be a chance to "step into a new life [and] create a new sense of purpose".
You've set 'unattainable' goals
With millennials more commonly having children in their thirties, our twenties have become the time to reach personal highs that would be all but inconceivable with a family to worry about, whether that's travelling around the world, or seeing something come to fruition.
I had always wanted to write a book, and, at 23, I managed to actually do it, forcing myself to overcome the self-doubt and taking the advice every author gives: just write the damn thing.
A month later I had my debut novel, Virgin, and by the time I was 24, it was published in more than a dozen countries along with a sequel. It was the achievement, rather than the financial benefits, that made me truly feel I'd reached a milestone.
You've looked after number one
"Self care" is the millennial mantra: 94 per cent said they made "personal improvement commitments" to looking after their minds and bodies in a 2015 study – but it's also the most adult thing anyone can do.
Having a massage isn't necessarily a sign of decadence, and nor is ordering a meal in at the end of a long day. Learning to make choices you know will relieve pressure during tricky times are all key parts of adulthood. There's no shame in asking for help.
You've parted with your smartphone
It is a rare young person who can survive an entire day without their mobile, but coping for a few hours without social media and 4G is the ultimate marker of millennial self-sufficiency. We're all so addicted to the highs of racking up "likes" on Instagram (four in 10 millennials say they interact more with their smartphones than with actual humans) that being able to disconnect is now a true sign of maturity. My current record is six hours.
You've failed well
We're dubbed the "snowflake generation" who can't take the heat when things get rough, but most of the time our so-called failures are simply a case of not meeting our own high expectations.
The biggest lesson I've learnt in my twenties is knowing when to try again after something goes awry, and managing my expectations so those "failures" do, in the long-run, become successes.
The Daily Telegraph, London