Like it or not, for most people Christmas means time with the family, a heavy meal in a warm house and the obligatory range of unwanted presents.
It's the season we love to hate.
People joke about how they will spend as little time as possible at their in-laws, swear themselves off the long trek home and pledge only to buy presents for the children or from charity shops next year.
For homeless people, with their high rates of isolation and loneliness, Christmas can be one of the hardest periods of the year, says Crisis chief executive Jon Sparks.
It can be "cold, lonely experience to be endured rather than enjoyed," he says.
But isn't this also true for many people who are not homeless?
Especially for those of us who are estranged from our families, habitually quarrelling with them, or simply a long way from home?
Perhaps that is partly why 13,000 people in the UK volunteer at Crisis centres where 7,200 mince pies, among other festive and nourishing items, are served to 4,000 guests.
Craig, from New Zealand, is no scrooge.
He will spend his festive break with homeless visitors to the Crisis's Christmas centre in Chalk Farm, north London, where 200 homeless guests will be fed, entertained and offered warmth and safety for a week.
"This is the first Christmas ever where I've been based in a city without family or close friends," he explains.
"I've been invited to a couple of 'orphan Christmases', but I've been feeling a little disconnected with London and it's the first time I've been able to give back, so to speak, on Christmas Day."
The 37-year-old came to London a year ago when he heard unexpectedly from his ex-girlfriend that he was going to be a father.
"So I came here because I wanted to be part of my child's life."
Mother and child have returned on their Christmas pilgrimage to New Zealand, so he thought volunteering might be a good cure for his isolation.
"I was feeling a little bit lonely, if I am honest.
"Christmas is all about belonging and being part of something and I thought that volunteering was a way to have that sense of belonging and helping out in other ways."
It's a similar story for Joana, 21, from Portugal, who could not get a flight home to Lisbon until Boxing Day.
She found out about Crisis on a list of "30 things to do at Christmas on your own".
"There was a lot of stuff I could have done, but I thought it would be good for me to do something that felt like I was contributing."
Richard, from Kansas City, who has been volunteering at Crisis for the last four years, says he got "addicted" the first time around.
"The big phrase that we use around here is that this is the Crisis family, and it really is like a family, as my real family is in the US."
He continues: "It's a hard draining week, but we get very close with the people we are working with, and we keep in touch throughout the year as well."
Martyn, is something of an institution at Crisis, having volunteered his winning smile and willing hands for the past 15 years.
He says: "Once you do it you can't go back to a normal Christmas - it's impossible, once you realise it costs nothing but your time."
As a homeless visitor limps past him, responding to Martyn's warmth, the veteran volunteer says: "A smile for somebody like that lifts them.
"When they come in here they're really down. They've probably been ignored most of the year.
"And you watch them gradually lift their heads up - they start talking and their communication skills come back."
And with homelessness rising by whatever measure is used, plus a 55% rise in rough sleeping in London alone, according to Crisis, the need is great indeed.
Charlotte, a former trader in the City, says giving up her time simply to do something for others is a "humbling experience".
And this sense of humility is a recurring theme among the volunteers and the centre users themselves.
One Lithuanian guest of the centre, who has been homeless for the past eight days, says: "In situations like this you realise that you don't really need very much at all.
"The material stuff, things like gadgets, positions in society, we realise we really don't need them."
Martyn explains: "This is Christmas. This is what Christmas is all about.
"It's not about all that commercialism, it's about living your life and saying maybe I haven't had a brilliant year, but compared to these people I've had a pretty good year."
As Crisis, the homelessness charity, opens the doors of its centres to an expected 4,000 guests, what motivates those who give up their Christmases to help out?