Half a century. 50 years old. Somehow the age of 50 seems far more significant than the beginning of any other new decade of life – and it’s the one I am reaching this week.

I’ve known it was coming for a while now but as the day itself approaches with frightening speed, it’s becoming more disturbing to my state of mind.

It’s in that grey area between young and old, definitely defined as middle-aged no matter how many times you hear people desperately laughing, “Middle age is always 10 years away!”

You are neither young nor old, neither important nor unimportant, neither visible nor invisible. In your head, you feel a lot younger than you are but your body tells you that time has caught up with you.

Middle age, to me, is the point where looking forward to whatever life still has in store for you is punctuated with worry about pensions (no, I haven’t got one), ill health (will I live long enough to see the children happy and settled in life?) and ageing parents, yet selfishly still wondering whether there will ever be the opportunity for me to go on the trips of a lifetime that I’ve always dreamed about.

What about that cruise down the coast of Alaska where you get to see whales in their natural habitat? The chance to see the Inca site Machu Picchu in Peru? The Himalayas? The Pyramids?

What’s most frightening is the thought that time might now be running out; that there’s a limit. In your youth, life stretches before you endlessly and that’s one of the joys of youth.

It’s what gives you a zest for life, an energy, an optimism, ambition, hope. But as time passes, one of the harsh lessons you learn in life is that life is limited. There is an end. Oh, you know that, of course, when you’re young – but in theory. It doesn’t seem real. In middle age, it suddenly becomes very real.

At 50, you start putting a number of years on the amount of life you may have left – it’s only 20 years until I’m 70, 25 until I’m 75 and so on.

It seems a paltry number of years when I can recall as a child thinking I had another half a century to go until I’d be the same age as my grandma. And I can remember my mother comforting me when she found me crying at around the age of five because “I don’t want to die!”

She said: “You don’t need to worry about that – it’s not going to happen for years and years.”

Of course, we wouldn’t all obsess about age and ageing if we weren’t constantly told that our age is such an important part of who we are.

Especially women: we’re bombarded with the message that to age is the worst possible thing for us, that we should buy expensive creams to make ourselves look younger or even have the old bits surgically removed or enhanced.

Ageing used to be an accepted part of life, barely talked about, the passage of time rarely regretted but that’s no longer the case.

Our age defines who we are and what we can do and dictates our place in society, so much so that we have had to legislate on it in many areas: work, family life (the age limit for foster or adoptive parents, for example), home ownership, even down to whether you can have a cat or a dog from the RSPCA.

Age creeps up on us. It doesn’t seem like it was just over 30 years ago that I was the youngest reporter in the newsroom on my first newspaper. Now I’m one of the oldest people in the newsroom at The Argus.

Well, the grey hairs are starting to show and my “golden years” as my daughter has been calling my impending 50s, are here. I could wallow in misery and spend the rest of my life looking backwards. But I’m determined not to waste them and to live life to the full. I’m going to grow old disgracefully.

The Argus:

See these “never-before-seen” pictures of Paul McCartney/Mick Jagger/any old celeb, scream headlines in national newspapers every five minutes.

Who cares? I don’t. There are millions of photographs of stars as old as the hills, whether they’re publicity shots, pap snaps or private moments – we’ve seen it all.

One picture of Paul McCartney in, say, 1966, is the same as another because even if we’ve never been lucky enough to see this particular one before, he looks exactly the same in all of them, except he might be glancing coyly upwards and to the right – and we’ve never seen him do that before.

The latest is, inevitably, David Bowie. There’s a new book of ‘never-seen-before’ pictures of him. And surprise! He looks just like David Bowie in all of them.