We all know the classic relationship destroyers: affairs, money problems, growing apart. But there’s a sneakier category of marriage-enders that nobody warns you about.No one sees these coming because they are ordinary life events. On paper, things like a house renovation look like a GOOD thing.But there is a common thread between all of them and a name for it: ‘identity drift.’This is when a life event changes one partner faster than it changes the other and you lose your shared view of ‘who we are’. Sometimes, the gap between who you were five years ago and who you are five years later becomes too wide to bridge.But panic not if you’re about to deal with any of these.Relationships can cope perfectly well with change – you just need to tell each other where you’re headed.Here’s the why and how to help you through. British sex and relationships expert Tracey Cox (pictured) reveals five forms of 'identity drift' that could be derailing your marriage - and how to work with them rather than against themRenovating your house Doing up a place together or finally moving to that bigger house in the suburbs sounds like something that would bring you closer not drive you apart.Truth is, renovating a property is one of the biggest relationship tests there is because it hits every trigger. If ever there was a team exercise designed to expose all your flaws, this is it.First up, your spending styles. You’re a spender, your partner is a saver. You want to go big, splash out on what you’ve always wanted; they want to get value for money and keep the savings stash healthy.What you each most value in life is also reflected on which things you want to spend most on. 'It became blindingly obvious what state our marriage was in when his must have was a "man shed" and all I wanted was my own bedroom,' one woman told me. 'We were trying to escape from each other in the same house. We divorced soon afterwards.'How you resolve differences of opinion is also highlighted. Who gives in to who? Who decides to fight to the death for pink walls but won’t explain what they’re really arguing about?How you both react when things go wrong – and they will – is telling. Do you play the blame game or act as a team?Ward off trouble: Constantly remind each other you are a team not opponents. Be fair: if one person gets their say on one thing, the other gets to make another choice. Keep asking yourself and each other: what does this represent for me/them? What are we really arguing about?Giving up drinking This is a biggie – but especially if both of you drink and only one of you wants to make a change.If you’re both keen to cut down on your units or stop completely, hallelujah! If you both drank excessively, doing this is almost 100 per cent guaranteed to improve your relationship.Not so much if you were a couple who loved wine and long lunches and loud, raucous, booze-fuelled dinner parties. However much you’re paying the price now (sick of the drunken arguments or bad health are the usual reasons to stop or cut down), they were fun back then.Things look very different sober. It’s a seismic change, startlingly so. I have been in this situation myself and also witnessed it often. Relationships are put under a lot of strain – and lots don’t survive.Life through sober and drunk eyes are very different.The partner who stops drinking gets clarity: about their marriage, finances, health, perpetual arguments. Often, they don’t like what they see.The partner who continues drinking feels self-conscious, judged and abandoned. The person they loved and married seems to have disappeared. The ‘fun’ has gone.Ward off trouble: Voicing your concerns before any changes are made is a good start. If that always causes an argument, try heaping on reassurance that changing drinking habits doesn’t mean you don’t love the other person. In lots of cases, it means you do. If you’re stopping for health reasons, you’re ensuring you will be around. If alcohol is causing issues, one sober person is better than two drunk ones. If it’s all going horribly off the rails, get couple’s counselling.A career pivot Feeling a bit uneasy that your partner is starting a new job? Your instincts are right: a career pivot or complete change can be dangerous to your marriage.They’ll meet new people, ones who will find your partner as interesting as you did at the start because they don’t have ten years history and old arguments attached to them. They also have the chance to reinvent themselves. Become a new version without all the old flaws. It’s intoxicating.Psychologists call this the ‘self-expansion’ effect. We’re invigorated by things that make us feel like we’re growing and changing. A long marriage can make us feel everything but.Do well and a whole new future you never dreamed of appears. Your aspirations are higher and you’re willing to take risks because your confidence has grown.It’s easy to feel left behind if you’re the spouse who isn’t doing anything new – or to be left because you suddenly appear stale and unappealing.Ward off trouble: The partner going through the change needs to actively include their partner in their new world. Compartmentalising – keeping this bright, shiny, new thing as their own – is what causes problems. Inviting colleagues home to meet their family sends a message: I'm taken and happy.If you’re one feeling left behind, meet your partner after work at his workplace and say you’d like to be introduced.Significant weight loss Of course you’re happy your partner’s finally shed that excess weight! But the same way you’re happy they got the job they always wanted, there’s a nagging anxiety behind the ‘Well done you!’A more attractive partner means newfound confidence and attention from others. If you were always the best looking of the two of you, suddenly your role is challenged. What if your partner decides they could aim higher? Get a younger, fitter, more glamorous version of you?Weight loss also means lifestyle changes. If you were both hedonists and enjoyed long, three-course lunches you might resent swapping that for a brisk walk in the park. If you could also do with losing weight but aren’t motivated, the pressure is on.Ward off trouble: If your partner has transformed, be honest. Say you think they look amazing but maybe too amazing. Ask for reassurance that the ‘new them’ will still want the ‘old you’. If you’re the person who suddenly has new options, think carefully before acting on any. More people regret leaving long-term partners than they do not acting on impulses.Caring for ageing parents It’s the least glamorous on the list but it changes people just as profoundly as any of the others.When one partner takes on primary responsibility for an ailing parent, they’re forced to become a competent, indispensable adult. It can bring out the best and worst in people.Some emerge feeling pretty good about themselves, proud of the job they’ve done. Others feel overwhelmed and ashamed of not being there the way they’d like to.Either way, caring for elderly parents is all-consuming. Your needs and your partner’s become secondary.Lots of marriages do not survive the lack of attention – others wither with too much. If the partner doing all the work realises their spouse is incapable or unwilling to look after themselves, it shines an unflattering light.On the flip side, it can transform an attractive, happy spouse into a carer who has no time to worry about their appearance, depressed as they face the looming death of someone they love.Ward off trouble: Have a frank conversation about how life will look for the next while, then be honest about what you both need. If she’s caring for parents, he can take over looking after any children, household chores etc. If you can possibly manage it, arrange one day a month where someone takes over to give you time together. If that’s unachievable go for a quick dinner out. Those tiny grabs of time together can save you.Visit traceycox.com or follow Tracey @traceycoxsexauthor.