How much do you spend at the petrol pump each month? What do you spend on eating out each month?

Such questions could roll on and on and - if you are like most of us - you would probably only guess at the answers.

But the failure to keep a close watch on your spending over the short and long-term is truly a bad habit and that could cost you dearly.

M.P. Dunleavey, a freelance journalist writing in The New York Times, recently figured with the overflow of negative news about the share and credit markets over recent months that she needed reassurance that her family's personal finances were in good shape.

"So I decided to take some of my own advice and read our household checking account statement over my morning coffee," she writes in a column this month.

"The standard personal finance guidance would be to monitor one's spending over a longer period of time, preferably by keeping a detailed money diary or using financial software. I have found that spending 10 to 15 minutes reviewing the bill payments, cheques, debit charges and other transactions in a single month can be just as valuable."

Far from gaining the expected reassurance about her own money management, Dunleavey was in for a rude shock.

"It is a nifty way to ruin your morning," she says. For instance, the Dunleavey family was paying much more than expected for their use of ATMs. And petrol presented another shock; the impact of higher petrol prices had been much underestimated.

"That's what my foray through our bank statement showed," she writes. "I don't know if the truth sets you free but staring your finances in the face, as opposed to devising convenient estimates in your head, is as vital to your financial health as checking your cholesterol is to your physical health.

"Bad eating habits and bad money habits have a nasty way of building up if you're not paying attention."

Personal debt control is something that we can all exercise - typically with great results. Why delay any longer?