And then, before I'd had a chance really to even contemplate what exactly I meant by this, I heard myself saying, out loud, but I am 35. Well, not that far off 35.
The this might have been the dependence on other people. Or the hours of public transport in any given day. (Five, on that particular day.) Granted, this could be resolved by the purchase of a car (and a few driving lessons), but I have no money for that kind of thing - which itself may be part of the this.
But the this goes deeper than that. Let me explain.
Just a couple of days after this standing-on-the-side-of-the-road moment, I was listening to the Rachel Maddow show, as is my political-junkie wont, and they mentioned her age: she's in her thirties.
I'm in my thirties.
Then Ed Miliband won the Labour leadership contest. (He's half-Belgian, by the way, a fact which has not been mentioned often enough, or in fact ever). He's forty.
That's only eight years more than me.
Where will I be in eight years' time? And my worry is this: shouldn't I be on my way there already?
I am frustrated. I know that I have the ability to excel at something. That if I could single-mindedly set my course, I could still get there, albeit a decade or two behind Rachel or Ed.
Wherever there is. And that's the nub of the problem. Single-mindedness is, by its very definition, exclusive. It takes, apparently, 10,000 hours to master a skill; that's 10,000 hours not spent doing something else. And I'm one of those people with "too many passions to pick just one": desperate to excel, yet trapped in what feels like mediocrity by the paralysis of choice.
Every week, it seems, a new dream job occurs to me: White House correspondant for the Guardian! Literary Agent! Manager of Social Media for a US Senator! The list goes on, and on.
And I just can't seem to choose one to the exclusion of all the others.
Besides, it's too late, isn't it? It's too late for unpaid internships and three more years of study and depending on the goodwill of people in London or New York or DC to house me for minimal rent. That moment was in my twenties, and I've missed it.
So I feel deeply dissatisfied. Purposeless. And frustrated because I feel like I could do so much more, be so much more, and I worry that I'm wasting my life and my abilities and just getting by.
I'd love to have a great, rousing, optimistic conclusion for you. I feel, though, that this post is just going to fizzle out. Sometimes I worry that my potential is going to do the same. I hope not. I hope that writing really is going to be it, in the end, whether that's journalism or fiction or both.
And the great thing about writing - aside from the excuse to spend a lot of money on funky stationery - is that it can encompass all your other passions. (There's a reason the hero in my novel has curly hair and dimples, and a reason why the heroine, who used to teach languages, and loves books, lives in DC and is a Senator fighting for better childcare laws.)
I loved the novel One Day, partly, I suspect, because Emma could be me. She has a good degree from a reputable university but is adrift in a sea of vague possibilities, never quite settling on what to do with her life, dabbling in teaching before realising in her early thirties that all she has ever wanted to do is write.
And maybe I'm being too impatient. Maybe writing is it for me, the thing in which I will excel, the way I will make my mark on the world. Maybe writing is my this. Maybe I just need to put in those 10,000 hours. But I'm standing at the bottom of my mountain, thinking that sounds like a lot. Looking at the Rachel Maddows and Ed Milibands who have been climbing since they could toddle, and getting discouraged at all the catching-up I have to do. Running to the foot of another mountain and then another and wondering if this one or that one would be more fun, more profitable, more me.
And while I'm running from mountain to mountain, wishing I had the right equipment to climb, time is slipping away, and I am becoming increasingly frustrated.