It's amazing how the simple act of returning to a place you once knew well can suddenly throw a spotlight on huge changes that have taken place in your life, changes that have snuck up on you without you noticing. Perhaps it's the roads and pavements - they stay determinedly the same from visit to visit and remind you poignantly that it feels different because you are different.
My trip to New York last week couldn't have been more different to the time I lived there on a student visa for four months six years ago. Yet the changes had little to do with the fabric of the city, as there was so much that was familiar.
The small impromptu garden on the fringes of Alphabet city, which I passed each day, is still thriving. The huge DKNY mural still dominates the crossroads of Broadway and Houston Street, just a few yards up from the giant fashion store where I used to work. The store itself, a monument to the overblown fantasy that was 1980s fashion called La Rue Des Reves: Your Street of Fashion Dreams, has gone, but there is a 1990s equivalent with a name like J.L. Yachting Co. in its place.
Sure, much greater changes have taken place - when I lived in the East Village it was a fairly grungy kind of place with its own low-down, edgy chic. Now there is a branch of that most WASPish of American chains, Gap and, at its heart, Tompkin's Square park has traded drop-outs and drunks for flowerbeds and playgrounds. Time Square too is uneasily clean, bright and full of lights instead of seedy, exotic and full of strip joints.
Yet there is an enduring quality to New York because its energy, its bright yellow cabs and its skyscrapers are always and ever the same.
But, again and again during my trip, I was struck by how different my experience was to the one I had six years ago. Money has much to do with it. Back then, the chief motivating factor behind any of our plans was cash and our lack of it. Subletting a tiny one-room apartment with two friends, we slept higgledy-piggledy like dogs in a basket and hunted endlessly for supermarkets, laundrettes or friends with air-conditioning where you could hang out for free.
We went out to bars which offered pitchers of beer for a few dollars and free jello shots, or restaurants that advertised all-you-can-eat deals. Shopping meant picking up a pizza slice for dinner or scouring second-hand clothes shops and huge consignment warehouses in Brooklyn for complete outfits costing under $5.
I felt that I knew New York well, yet never ventured uptown unless it was to watch the rollerbladers in Central Park. Uptown seemed expensive, repetitive and terribly dull.
It was all quite different the other week. Rather than having to weave my way through the local junkies to get in my front door as I did in the East Village, I had to deliberate as to exactly how much of a tip the doorman expected as he waved me into yet another posh uptown apartment block. There were meals that were long, extravagant affairs in trendy restaurants or chi-chi downtown cafes, while drinking was done at cocktail parties where people tut-tutted about how downmarket Tiffany's had become or how short the Hamptons season was.
Of course, it wasn't all parties and glitz - there were a fair amount of grotty Brooklyn bars, seedy nightclubs, cramped apartments belonging to friends and bagels and cream cheese. I hadn't actually bought into this whole world - which is thankfully out of my league both financially and emotionally - I nearly snorted champagne out of my nose when one Texan millionaire drawled "Ireland is so wunnerful: I used to get all my horses made there."
It was more a question of access - on this trip I knew where these parties were going on and could choose to go along and wonder at the brittle, thin, shiny glamour of it all, without worrying that my name wasn't on the guestlist or that everybody would take one look at me and shout "Imposter".
One evening, as myself and a couple of Irish friends were in a cab whizzing along Madison Avenue between a party in a jewellery store and dinner in an uptown restaurant, we fell to musing about whether we had ever taken a cab when we came to New York first. "Do you know," someone said, "I feel distinctly traitorous to my East Village roots at parties like those. Is that ridiculous?"
It's not ridiculous but it's a very twenty-something moment. Within a short space of time, your life changes quite radically - not for better, not for worse, it just changes. Things become possible that would have been completely unheard of just a few years before - whether it's groovy parties and cabs everywhere or the ability to walk into a crowded room and not feel embarrassed. Being part of the working world plays a huge part: not only does it give you money to do things but it also provides a larger sphere of reference in which to place things. Yet there is also a sense of abandonment, even of treachery as my friend pointed out. Those times were good, so why the hurry to leave them behind? I sometimes think uneasily of my blissful memories of living on a beach in Honduras on an ample budget of $20 a week. I was full of idealism about how one should travel only with a toothbrush or a paintbrush, but never a hairbrush. Could I do that again? Would I want to?
Yet in New York last week, I realised that I had earned more than money in the past few years. Although I had a blast as a 20-year-old in New York, I also remember being swamped in awe of the insouciant, dead cool, downtown New Yorkers. Whatever they did, they did it better, it seemed to me then. When I went back a couple of weeks ago that awe was gone, replaced by a sense of celebration of their strengths and amusement at their oddities, a sense, really, of myself. And I wouldn't trade that for the world.