BIRTHDAYS, you will have been led to believe, are forever associated with celebration.

I've had a few of them now and I'm still puzzling over why.

Are we saying: "Congratulations, you're still alive"? "Thanks for being here, we're glad you were born"? "Look at that, another year closer to death"? Should your mother get the presents, given that she did all the hard work to get you here? It's a puzzle.

Birthdays plunge me into a great fog of dissatisfaction. It started on my 19th with a deep trepidation about leaving my teens. You could get away with just about anything by blaming it on teenageness but 20 seemed, like, totally old. Now 20 seems, like, totally a long time ago.

A general feeling that I've under-achieved my way through life thus far is compounded by another year gone and not much changed. Yet another year where I failed to unpick life's great mysteries: God, the universe and karaoke.

This year I feel particularly panic-stricken about my birthday, and not just because I've discovered I share it with Mick Hucknall, most loathed of all loathed pop stars.

Suddenly, I feel not young anymore. Not old, just not young. "You have come to realise your mortality," says my friend Shona, "and that one day you will die."

But I don't want to die. I hate missing out on things. It's like there's an enormous egg timer of life and the sand is drizzling away before my very eyes. Most people spend their birthdays looking forward to nice presents. I will be spending mine trying to shove over an invisible egg timer. That can't be normal.

I can't stop thinking about the unnegotiable finiteness of it all. The realisation there is no pause button on the relentless slideshow of years. If I think about it long enough it becomes a struggle to breathe, what with the rising panic and Ma Stewart clipping me round the ear for being so ridiculous. Life's short, eh, but what to do with it, how to make sure it's not wasted?

After extensive questioning the only benefit of age seems to be not worrying about offending people. I offend people all the time so it will be nice not to worry when it happens but it doesn't seem enough of a pay off.

Fortunately, there is one saving grace of birthdays: cake. There is no pause button, but at least there is cake.