This time of year is all about families getting together and celebrating what's important. However, there's another element to a gathering of so many adult relatives for Christmas.
It's called "revertigo": when people slip into old patterns from earlier in their lives.
You may already know the drill – your grown-up children revert to bickering over the roast turkey, or maybe the youngest is still deemed the "favourite", so all hell breaks loose. Perhaps you and your siblings even go at it like old times!
For those few days together, it's as if everyone forgets they're all well-functioning, responsible members of society, and instead they're back in the sandpit.
But don't feel like it's just your family – Relationships Australia reveals that a high proportion of people feel their family relationships are negatively affected at Christmas, despite all the joy to the world.
So why can this happen?
No matter how much time has passed, returning to the family home can be emotional. Unsurprisingly, people fall back into the "games, dances and dynamics" of old relationships, says Sydney-based psychologist Clare Mann.
Memories are dragged up, the same stories and in-jokes are rehashed ad nauseum, and long-standing disagreements resurface, adding to it being such a high-pressure time of the year.
"It's almost like suddenly everyone's on autopilot," Clare explains. "Our defences come down, especially if we've had a drink, too, and we slot back into that old way of being."
Neuroscience may also have something to do with old habits and behaviours cropping up.
Turns out that even when people have the very best of intentions, sometimes patterns are hardwired into our brains.
Research even shows emotions can be elicited from different environments, so something as familiar as a childhood home can be a powerful trigger for some people.
And, like many of our family histories, that can mean the good, the bad and often the downright complicated!
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Smell is another evocative prompt for rebooting memories, according to the journal Cognition and Emotion. Once you throw in sleeping in a childhood room or backyard cricket, it can be a fast track to a psychological minefield.
"People slide back into those roles and then buttons get pressed," Clare says.
"This is because our unconscious intentions and behaviours can be more influential than our conscious desires. Our brains are so used to being a certain way with our families that it just slips and slots us back into that old routine."
Even if that's not what you really want.
Every festive season is filled with so many expectations for things to be perfect. Guess what? That's not going to happen! Perspective is key.
"This year, ask yourself what you'd like to get out of Christmas with your family in an ideal world," Clare says. "Then, after looking at your family's history and reality, ask yourself what you're likely to get. That way, you're not setting yourself up for disappointment."
It's also worth rethinking how you approach others. If you're expecting someone to act in a negative way – and treat them as such – they'll probably play up to that.
"We can't change the world, but if we change ourselves then we change our world, " she adds.
Change starts with you. So if you fall into patterns that no longer make you happy, remind yourself that it's alright to let go of the past and not play that role anymore.
Perhaps your family may create some wonderful new habits and rituals as adults that last a lifetime.