Here's why you should leave work and go on vacation — right now

Feel your brain switching off as work task upon task piles up around you?

It's time to stop.

Seriously: Turn off your computer and take a personal or sick day. Or — if you're lucky enough to have an understanding boss — request a last-minute vacation. Then GTFO.

Those itching to play hooky are not alone.

More than half of workers (54%) say their focus is switched or "clicked" off by Dec. 16, according to a new survey of 3,000 workers in the United Kingdom by human resources analytics firm Peakon.

Makes sense. Beyond the typical winter blahs, as the holidays approach, your thoughts turn to stuff like last-minute gift prep — and fun.

A little break could be justified even from your manager's perspective, since studies show overworked employees are less effective in the workplace, whereas happy workers are more productive.

Just ask for time off in a smart way, says hiring management expert Alison Green. Be normal — friendly, polite — and make it clear you have a plan in place so your boss won't have to stress, she said.

You could say something like, "I've given my cell number to my clients so they can still contact me while I'm out," Green said, or you could enlist a coworker to cover you for the days you take off.

"Do that thinking" for your boss before you ask, Green said, and you will be more likely to hear a "yes" in response.

And don't feel bad if you have been feeling checked out for awhile.

The Peakon survey found younger workers get distracted even earlier than their older colleagues. More than a third of employees aged 18 to 24 say they lose focus by Dec. 12, and two in three reported a mental check-out by Dec. 18.

Still nervous about asking for time off?

Remember, time is money — literally — and losing vacation days at the end of the year is equivalent to leaving cash on the table.

Plus, you'll have plenty of opportunities to make up for lost time in the new year. If December is the worst time to get stuff done, there's a great case for working through August — when the office tends to be quiet and there are fewer productivity-killing distractions.