To the young, 21 is a coming of age filled with energy, parties and the anticipation of life beginning. 40 is the swift descent into middle age where saggy jowls sip tepid cocktails before dashing home to relieve the babysitter of her charges.
30 is somewhere in between.
I am not the first of my friends to turn 30. Those who have already entered their fourth decade have done so with a quiet dread which I struggle to understand. To them ageing is something to be feared rather than something to be thankful for.
I remember my father raising a glass to my bright future on my 21st birthday. Less than a year later I'd be diagnosed with cancer and with it would come pain, a hearing impairment and worst of all, the realisation that none of us are immortal.
Lynsey (second from left) at her 21st birthday party.
I look back at those birthday photographs and can make myself believe that I haven't changed at all. But there are scars which go unseen which remind me that I didn't change at 21; it was the entire course of my life which changed.
So many say cancer was the best thing that ever happened to them but cancer was not the making of me; it was the making of a version of me. Who knows who I could have been without that tumour.
I can't tell you when I went from me, normal 21-year-old at university to me, normal 21-year-old cancer patient. Except there is no such thing as a normal 21-year-old cancer patient; we're a rare breed. A dying breed if you will.
Treatment felt never ending; there was tumour debulking surgery, chemotherapy, liver surgery, a tandem stem cell transplant and then another liver surgery. I don't refer to it as a fight because I was not the one who was fighting. War was waged between cancer, cytotoxic drugs and the surgeons wielding their knives. What was I but their battleground?
During that time I thought about death a lot. I found myself thinking in terms of years. I thought about dying at 70, 60, and I thought, you know, I would take that. I wondered - would 25 years be enough?
Maybe when still in the first 20 it would seem sufficient, but what about when it got down to those last five, when death could be seen screaming out of the shadows like a truck with its headlights on thundering down the motorway. Would it seem enough then?
Lynsey and her family just before she began chemotherapy.
I spent my 20's being broken, but I am not damaged. The remains of a vampire's kiss trail down my neck; scarring from central lines where blood was taken and drugs given. This leads to more carvings which are all that are left to hint at the cancer once within. There's a certain beauty to them; an art. I can see the surgeon's skill embossed upon my skin. I cried with relief when I woke to see the scar gently circling round my navel rather than through. It is a gift.
Once treatment finished there wasn't some great transformation; butterfly from the cocoon or sunshine after the rain. I mean, if you want some imagery, it was more like a phoenix rising from the ashes. You are ground down, put through the fire, and come out the other side, frail, wrinkled, bald and burned. Croaking where you once sang, trying frantically to remember what you once were, so you can attempt to claw your way back.
At the end of it all I didn't even have a decent adjective to hold onto from my oncologist - I can't tell you that you're in remission because for you, that means we expect it to come back. But I can't make you any promises or tell you that you're cured either; this is the closest you're going to get.
For many, 30 is full of fear and the realisation that life doesn't last forever. But if I'm honest, totally honest, I never thought about 30. I didn't worry about not seeing it because I was more concerned with surviving till 24. 23. Christmas.
Now I'm here; the goal is in sight and I'm baffled. I look in the mirror and I wonder how I got here. My friends cradle their children, their partners, their pets and I cradle the simple joy that I did not die.
30 doesn't force me to acknowledge my own mortality because I have already stared it down. At 30 I have stopped bargaining and instead I am living while I am alive.
You can keep your anxiety about growing older. 30 isn't an ending; for me it is the beginning.
Life Less Ordinary is a weekly blog series from HuffPost UK that showcases weird and wonderful life experiences. If you've got something extraordinary to share please email ukblogteam@huffingtonpost.com with LLO in the subject line. To read more from the series, visit our dedicated page.