I'm going to start with a question. And if anyone can provide an answer my bank manager will be eternally grateful.

Why is it that I am unable to walk past a shop covered with SALE posters without feeling the need to go inside?

The obvious answer is that, like most people across the country, I love to bag a bargain. And with the January sales in full swing, it's the time of year to buy, buy, buy.

But when you start racing towards shops you would never normally enter (or notice), stocking items you neither like nor need, it starts to become a little worrying.

Last weekend, I found myself in a mobile phone shop, as alien a territory to me as the Polar ice cap, looking at shiny new mobiles the size of matchboxes which can download 667094KWG per minute, write, direct and edit blockbuster films, make Sunday lunch and still have room for a keypad just in case you need to ring anyone.

I have a mobile already, albeit a vintage model, and I really don't want another. But it was, said the sign, HALF PRICE.

What if, I thought, in two months time, mine broke and I was forced into buying another. Then I would have to pay full price - and that would be silly.

Somehow, I found the inner strength to resist and head out, only to be confronted by a gigantic sign offering even bigger, MASSIVE SAVINGS. A hat shop. Do I ever wear a hat? Do I need a hat? No on both counts.

But, I reasoned, with MASSIVE SAVINGS - not only 50 per cent, I discovered, but 70 - I could be persuaded. I went so far as to try one on, but was saved by my youngster daughter, who piped up: "You look like an old granny."

Normally, when out in town, I do only what is necessary, pick up one thing, collect another, pay in this, withdraw that. Occasionally, I might buy the odd item of children's clothing, but rarely do I look for myself and, because money is tight, I always think hard about any purchases.

But at this time of year, common sense flies out of the window. "I don't need it" becomes "I might need it", and "I can't afford it" becomes "It's so cheap". And the bigger the saving, the more satisfying it is to buy. "Look at what it was before," I will say, pondering rods and lines in an angling supplies shop (I haven't quite gone that far yet, but give me time).

Even in the supermarket, I am drawn to the festive leftovers, all "drastically reduced" - selections of biscuits for cheese, trays of nibbles and snack sausage rolls (that I freeze for children's pack-ups - some things do "come in").

What many sales shoppers fail to notice is the cost of bagging a next-to-useless bargain can stack up. Before you know it, you've spent next month's mortgage on a dishwasher that doesn't fit into your kitchen, a leather corner sofa that takes up the whole living room, 15 electric toothbrushes (great birthday gifts, and such a good price), two waffle makers and a year's supply of rye crackers.