There is this thing we say when we bond with people on holidays. "We'll keep in touch," we promise.
This is what we really mean: "The last thing I want to do is keep in touch. I have enough friends in my life, and it's difficult enough to meet them for coffee these days, never mind trying to fit you in, too. And, anyway, you were grand for a week in Marbella over cocktails, but I don't think I could stick you back home. Your laugh is so annoying. Did you know that? I'd rather keep in touch with the Spanish waiter who kept saying: 'You big girl, eh? You eat sooo much.' And that's saying something, because I wanted to kill him."
Let's keep in touch. What we really mean is: "Let's resolve to lose each other's e-mail, Myspace or home addresses and phone numbers. Let's avoid eye contact if we ever happen to bump into each other on Grafton Street. Let's reminisce privately about the night we sat up till 4am at that beach-front bar talking about children's TV programmes from our youth - 'I mean Zippy and Bungle! They were so on drugs!' - and then lie to ourselves, saying what a shame it was that we never kept in touch."
This doesn't just apply to holidays, of course. Those people you were stuck in a lift with: remember how seriously you spoke about an elevator reunion? And that girl on the "finding yourself" trip to India who had soul sister written all over her? You only shared a couple of chanting sessions in Rishikesh, but it felt as if you had known her for several lifetimes.
How long did it take before that scrap of paper bearing her number found its way to a corner of your rucksack so that, when you got home, it was an indistinguishable piece of pulp that you shook into the bin with the used train tickets and assorted debris? Wish you'd kept her number now, don't you? No, not really. Too many existing friends and family, too little time.
"Let's keep in touch," we said to K, the human firefly we met at the Personality Cafe, which was part of Dublin Fringe Festival last year. She was an actress from Glasgow who had wandered off from the rest of her company when the play she was in - "rubbish play, terrible," she cheerfully admitted - closed.
We took her to dinner and made up songs in the rain-soaked Spiegeltent and brought her home, where we drank vodka and chatted until 5am as if we'd known each other all our lives. Let's keep in touch.
My boyfriend and I didn't tell many people we were going to Glasgow for the weekend. They might have asked questions. Such as, why Glasgow? Do you know anyone there? And we might have had to answer.
Glasgow is where K is from. Do you remember that girl we met once in the Personality Cafe? It felt as if we had known her for years. We said we'd keep in touch, so now we are going to visit her. The one person we told said: "So basically you are going to Glasgow to visit a stranger?" And we didn't really have anything to say to that.
It was another last night for K. Her play - "brilliant play, bloody great," she beamed - had finished its run. Come to the Butterfly and the Pig on Bath Street, she said, so we did, all the time wondering whether she had meant it when she said we should keep in touch. It was a big night for her - she had just bagged herself an agent - and she was celebrating with the cast and crew.
We drank Red Bull to give us wings and went to a house party on the top floor of a tenement where the actors danced to Dusty Springfield and impersonated the Artful Dodger (RIP).
We couldn't tell yet if, like us, she had meant it when she said to keep in touch. The next evening we went to dinner with K and her boyfriend in a Russian restaurant where we ate beef Stroganoff and blini. The chat flowed but was ever so slightly strained, taut like the strings on the classical guitar plink-plonking away in the background. Later we took a cab to the West End, where, after a drink, her boyfriend had to leave, to finish some work. And then there were three.
Small talk had reigned thus far. When I heard myself asking "Seen any good films lately?" I worried that we might be in trouble. But with just the three of us the talk turned to real things. She explained how she was facing an exciting time in her life, a chance to move to London, an opportunity to really make a go of her acting career, but how following her dream meant she might have to leave her boyfriend behind. And suddenly the thread that bound us together at the Personality Cafe was back, and I don't mind admitting it was a relief.
"I still feel like we are soulmates," she texted later. We've promised to keep in touch.