The Christmas lights are twinkling, the mince pies are made, there's Christmas music in every shop - and your relationship is quietly unravelling.

For all its magic, Christmas is one of the highest-risk times for couples.

Lawyers call the first Monday after New Year 'Divorce Day' because it's when they're inundated with enquiries from couples who barely made it through the holidays.

One UK study found, in the run-up to December, 39 per cent of married people admit to worrying about their marriage. Eight per cent think Christmas might be 'make or break'.

Why? Because Christmas brings together every major stress known to relationships: money, families, alcoholhigh expectations and no escape. Add exhaustion and a dash of nostalgia, and you've got a potent mix.

Here are six of the most common things that could derail your relationship this Christmas - and how to make sure they don't.

1. CRIPPLING COST OF CHRISTMAS

Emma and Dan decided to 'go big' on gifts last year - expensive gadgets, designer PJs, high-end candles. Emma didn't want to disappoint her parents (who expect 'next level' presents). Dan felt anxious but went along with it.

'By mid-December, every conversation was about how much I was spending and ended in a big row,' Emma said.

'By Christmas Eve, we weren't talking at all. My parents didn't even notice the posh presents; they were more worried about us ignoring each other. I won't repeat that mistake.'

Research shows more arguments happen in December than in any other month. A lot of them are about the level of spending.

How to stop the rows:

Obvious but hardly ever done...

Set a clear budget together - early. And make sure it reflects your financial situation, not what you think you should spend on family and friends.

Suggest a secret Santa to reduce the overall spend. You aren't the only couple struggling with money. Most people are relieved when someone speaks up and suggests a cheaper option.

Don't equate money with love. If your partner's present to you didn't cost as much as you spent on them, it doesn't mean they love you less. There are so many other factors at play.

Make it personal, not expensive. How do you feel when you unwrap a present that hundreds of other people will also unwrap? A present that costs less but shows you really get the person you're giving it to will be appreciated far more than that expensive perfume (of the moment).

2. THE END OF YEAR RELATIONSHIP REVIEW

Christmas and New Year force reflection. You slow down, look back and sometimes don't love what you see.

If you've been struggling, chances are one of you has set this time as a deadline. 'If we're still arguing by Christmas, there's no hope.' 'If he's still drinking as much, he's out.'

Even if you're not having issues, it's normal to take a mental inventory of your life. 'Where are we?' 'What have we achieved?'

Social media and family gatherings mean there's high visibility of other people's lives, which can trigger serious reflection and introspection.

Turn it into a positive:

Don't launch into big relationship talks, both drunk, on Christmas Eve. Instead...

Pre-empt what's coming. Don't wait for it all to blow up. If you're getting on well, say, 'I love us and I'm so happy we get on so well. This is probably a good time to do a relationship MOT. Shall we both think about what we love and don't enjoy so much about our relationship, so it's even better next year?'

If you're going through a rocky period, say, 'I know we aren't seeing eye to eye right now. How about we both think of what we think is causing it and then have a chat to clear the air?'

Keep it positive. Recognise that Christmas is stressful and that relationships are hard. Your relationship might not be failing; it might just need recharging. Again, it's normal to argue more this time of the year.

THE PRESSURE OF PERFECT HOLIDAY RITUALS

Couples who have meaningful Christmas rituals - like decorating the tree together - are happier than those who don't. If you didn't feel pressure before reading that, you probably will now.

Blame the media for high Christmas expectations. We're bombarded with ads of happy families (perfect nuclear ones), expertly decorated trees and lavishly laid tables.

If yours don't measure up to create the 'perfect Christmas', there's disappointment - and conflict. It's called 'the expectation gap': When what we expect from an event wildly exceeds what real life delivers. The bigger the gap, the bigger the disappointment - and the more likely we are to blame our partner.

Interestingly, studies show it's not just taking part in holiday rituals that makes couples stronger, it's finding meaning in them together. 'Go on, you always get to put the star at the top of the tree,' kind of stuff.

If one partner's left to do everything, it turns into an obligation, and resentment builds.

Fix it by:

Having each other's backs and being gentle with each other.

Tell the stories behind the rituals. Why does your partner insist on dragging the kids out of bed for midnight mass when he doesn't set foot in church any other time? Why does she drive across the country to see a relative she never sees the rest of the year?

If you know midnight mass is where he and his mother went after his father died, and she found it a comfort, suddenly it makes sense. That ignored relative visit might mean a lot to her parents, who can't make the trip themselves.

Share the load: God, I hate wrapping presents. I love the idea of it but after wrapping one, I'm bored already. Making Christmas a nice experience takes a LOT of work. Split the tasks. Make sure one of you isn't shouldering the whole burden.

Laugh if things go wrong. Guests arrive late, the turkey's drier than firewood, you forgot to serve the dish that took ages to prepare, you're snowed in, and you can't get to anyone and they can't get to you. It feels like a disaster at the time but if you laugh, you'll be telling the story for years.

It's not a competition. It's meant to be a time for warmth and togetherness, not showing the neighbours how great your place looks compared to theirs.

MANAGING FAMILY DYNAMICS

The 'who spends Christmas where?' drama is often the biggest stress of all. You're juggling four sets of expectations: what could possibly go right?

A friend of mine is facing her first Christmas with her new partner - and their first major disagreement. His family usually arrive on December 23 and leaves the day after Boxing Day.

She always hosts Christmas and would be gutted not to be the one entertaining the masses. 'I seriously don't know how to play this,' she told me. 'My parents are quite old. Is it worth upsetting them to appease a guy I've only been with for six months? I'm torn.'

Fix it by:

You can't please everyone; it's impossible. But you can make it easier by...

Planning early. Decide together what you want to do way before anyone asks. Where you'll be, when you'll travel, who gets to stay/who you'll stay with and who is invited.

If Christmas is always fraught, have these discussions in October. I'm deadly serious. You both then have time to get used to what's proposed and time to carefully think through how to word difficult conversations.

If something isn't going to be the norm, tell the people concerned early so they have time to get used to it as well. Springing a change on people last minute is never a great idea, especially if they're old.

Split visits fairly and set boundaries. Make sure both are clear on family routines and traditions and what they'll likely expect from each of you.

If one of you baulks at something, find a compromise. Don't forget to carve out some time for just the two of you. A morning walk, a coffee in bed, popping to the shops together to grab something - being able to vent, even for minutes, diffuses a lot of tension.

Remember the golden rule: you're allowed to criticise your own family, but they aren't. His sister's being a right pain? Let him complain. You're allowed to agree but don't jump in gleefully.

IT'S JUST ALL TOO MUCH

Work stress, family obligations, drinking and eating too much, not enough sleep, a house full of guests (who all seem to be watching the two of you do everything), choosing your partner's present with care and love and getting a hasty last-minute thing in return....is it any wonder you're irritated with each other and feeling hard done by.

'We have three kids under ten. In one week, we had a children's nativity play, drinks with neighbours we don't even like, the boiler broke, work was crazy, my Mum got really sick, and my boss was on my back for not finishing what I was supposed to,' one harried mother told me.

'My husband had a go at me for not getting enough wrapping paper and I exploded! If I could have divorced him and walked out on all of them on the spot, I would have.'

Calm it down by:

Acknowledging you're both under pressure.

Don't pretend it's all 'fun' when it isn't. You're better off saying, 'I would give up wine for a year if I could not go to this party tonight', than pretending and snapping at your partner all night. It's a messy, stressy time of year.

Do something together that you both enjoy. If you're really suffering, pack the kids off to your mother's for a few hours and go for a walk or to the pub for a drink and a recharge. Or do something that always resets you as a couple. Though having encouraged you to go to the pub.....

Watch your drinking. Having one drink might relax you, but having four can alter your mood - and not in a good way.

Drinking every night takes its toll on our bodies and mental health. If you're drinking a lot and arguing just as much, take a few days off to detox. You might be surprised what a difference it makes.

You'll find Tracey's product ranges at lovehoney.co.uk. Traceycox.com has info on her weekly podcast, SexTok. Her latest book is 'Great Sex Starts at 50'.