Christina Patterson: There's nothing like the kindness of strangers

To the man from Virgin, who, on hearing that two sim cards hadn't arrived, and being told that getting, finally, to speak to a human being was an achievement virtually unmatched in any other sphere of my life, and one that could not necessarily be repeated, agreed to call me to check if the card had arrived, and did so, several times, until I could assure him that it had, thank you.

To the woman at A & N who, when I tried to buy yet another black coat, gently steered me to a purple one, which I wouldn't have chosen in a million years, but which definitely made me look less like the Death character in The Seventh Seal, when there was nothing in it for her except the momentary satisfaction of a pallid face made slightly less pallid, thank you.

To the man on duty in the changing room at Zara who tried to get me to smile and told me to be happy and, when I told him that it was rather tricky at the moment, insisted on giving me a discount on the jeans I was buying, even though they were only 20 quid, and marched up to the till to make sure I received it, thank you.

And to the many readers who have written to me this week, after a column I wrote about my day at a breast cancer clinic last week, thank you. I've been trying to work, damn you, but every time I switch on my laptop there's another name I don't recognise in my inbox, and another precious slice of empathy.

One reader invited me to a concert next spring. Another sent funny pictures to cheer me up – and they did. Several have offered shoulders to cry on. Some have even quoted my own columns back at me, reminding me, as I apparently wrote recently, that "anger is an energy" and that being able to live with life's darknesses can help to bolster resilience when faced with crises. (Did I say that? Well, I didn't mean it, obviously.)

One said, simply, that he didn't want me to die. That one made me cry. Well, to be honest, they nearly all made me cry. I wrote last week's column as soon as I came back from the hospital, in a white heat of rage and despair. I didn't quite believe it, and I thought that writing it down might make it real. Emails from people you haven't met saying they don't want you to die do indeed make it real.

This week, more than any other in my life, I've been moved by the kindness of strangers. I've been struck by how people we don't know can bring out the very best in us, and also the worse. It's sometimes quite hard to be polite to the cold caller who interrupts your precious, longed-for sit-down with a glass of wine with an interrogation about your mobile phone contract, or the kind of windows you have (er, glass?) and sometimes you don't want to. Sometimes, it's a handy outlet for steam from an awful day. You don't know them, so what does it matter?

It matters, of course, for one reason alone. Other people are real. We only ever treat someone to a gratuitous onslaught of rage, or jobsworth apathy, if we forget, for a moment, that they're as real as us, as likely to be upset as us, as likely to have their day wrecked by the rudeness of a stranger as us.

And we only ever offer to return a phone call, or help someone choose a coat, or give them a little discount to cheer them up, or write them emails that are warm, generous, affectionate and bursting with kindness, if we remember, if we know in our hearts, deep in our hearts, that this is a person like me, that this would make me feel better, and I will do the same for them. It's why the New Testament update on the commandments, "do unto others as you would have them do unto you", remains the only moral message we'll ever need.

Strangers are a kind of liberation. They can set you free to be anything you want, to behave badly or to behave well, in ways that are habitual, or that are suddenly, magnificently, out of character. It's one of the reasons I love cities. No twitching curtains, no did-you-see-what-time-she-came-back-last-night, no stifling sense of you must do this.

If you think, for some strange reason, that village life is some kind of utopian ideal of a human community then just go and see The White Ribbon. I did, on Sunday night, and came out thinking that the circumstances of my life really weren't that bad. Michael Haneke's tale of rural repression and suppressed sadism may not be entirely representative of small communities and how they function, but it's a reminder that a community is only ever a community. Only as good or bad, or kind, or unkind, as the people in it.

I'm already sick of this bloody illness, and I've only just started, and I've got a very long way to go, so I'll sign off now and shut up for a while, but to all these people, for all these kindnesses, and to the best readers of one of the (still, on a shoestring) best newspapers in the world, thank you, thank you, thank you.

c.patterson@independent.co.uk