By BECKY BARROW

Last updated at 10:01 21 January 2008

The weather is appalling, the Christmas credit card bills are landing on the doorstep . . . and you've already broken your New Year's resolutions.

But don't worry, if you can just get through today, things will start to look up.

Monday, January 21, you see, has been officially declared the gloomiest day of the year.

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Psychologist Cliff Arnall, an expert in depression, has used a mathematical formula to pinpoint today as Blue Monday.

He says it is the day when six factors come together to leave us at our most miserable.

They are: the dank and gloomy weather; Christmas debt; a feeling of monotony after the Christmas cheer has faded; broken New Year's resolutions; low levels of motivation; and a desperate feeling that you need to take action to improve your drab existence.

Millions are also still struggling to get back into the routine of working after a long Christmas break - and many will not have their next holiday until August.

Blue Monday may be compounded by the fact that, according to other research, many people get their worst night's sleep on Sunday because they dread the prospect of going back to work the following day.

Mr Arnall, a former academic at Cardiff University, whose research was commissioned by personal development company Advance Performance, said one of the best ways to beat the blues was simply to stop moaning.

"If you are a regular whinger or moaner about the weather or minor ailments, stop," he said. "It is boring and you are boring.

"Focus on the good things you do have in your life. If one of your limbs does not work, focus on the three that do."

Other tips include: stop seeing those you do not like; start saying "no" to unreasonable requests; and help others by doing voluntary work.

Researchers say many workers lose up to one hour's sleep on Sunday night because they hate the idea of returning to work on Monday morning.

Difficult bosses, looming deadlines and important presentations can all keep workers awake on a Sunday night.

The best night is Friday, when the working week is over and many are looking forward to the prospect of a relaxing weekend.

Leigh McCarron, of hotel chain Travelodge, which commissioned the research, said: "Millions of workers are starting the week tired and unmotivated.

"One in ten say their sleeping patterns are at their worst in January as they return to work after Christmas and feel unable to cope with increased workloads."