I’d go the other way and not try to “feel Christmassy”. Your list of negatives is pretty long and persuasive.
This is my first Christmas since my mum died two months ago, and I’ve been unable to see my DB’s family in over two years due to covid (they are overseas). These are the only true blights on my life but to me they are big ones, and I’m sad. I’m not pressuring myself to do anything I can’t handle and I’m allowing myself to be quiet, downbeat and to cry, except for when I’m around my kids.
My Christmas has consisted so far of a series of small meaningful things - charity donations, writing letters and cards to my mum’s friends, going to church to pray, putting up a Christmas tree, eating stollen and elderberry wine (a traditional thing for me), making my mum’s Christmas pickle.
I don’t think we need to feel Christmassy in the commercial, “have fun every minute” way. I think we can reflect on the Christian side of it, even if we aren’t all Christian. It is a message of hope in the world, and sometimes that’s the most important thing to hold on to, to keep our strength up.
Your exSiL might relent and realise her kids would benefit from family continuity, if you are not judgemental and you send the message you want to stay in touch.
Your new job is unlikely to be rubbish. It’s a busy time of year, so HR and payroll teams are slammed due to early close for Christmas payrolls. You can be added to a payroll any time in first half January and still be paid, I expect.
Your old colleagues clearly repent being awful and now are trying to make up for it. Let them, then put the whole sorry mess behind you.
Go on a social media diet. Stay away, or only read the homepages and feeds of charities. You’re comparing yourself to a tiny minority of influencers, you’d be more grounded if you compared yourself to the millions of people in dire distress for one reason or another.
I can’t help you with the absence of your own kids, that is a tough one. I’m sorry, I can imagine the pain and dissatisfaction that causes, and although I will say it is easy to idealise life with children, I cannot imagine the emptiness of life without them.
You can have a belated big birthday celebration. If you can’t be with family and friends on the day itself, then make the most of the isolation and spend the entire day in bed together having wild uninhibited sex.
And 2022 doesn’t have to be so gloomy. You can fix the lack of friends. You could even plan to move again! And if you can’t plan holidays then what else could you do with the money and time saved? A million things, I could make you a bucket list but you’d be better off making your own wish list. Sensible things. Crazy things. Things to help other people, our family but also far beyond. Things to help yourself.
These are problems you can solve, they are within your control. You can make a difference in your own life. People are by nature restless, so use that energy to do something positive, instead of turning it on yourself destructively and berating yourself. The smallest win is still a win. And even a failure is an experience you can learn from and move on from.
Make your life a collection of little wins (“i got a new job, my DH loves me and wants to have a child with me, I have some beloved nephews/nieces whose lives I want to find a way to stay part of, I made beans on toast for lunch and it tasted SO good I’m going to go vegan for a month and donate all the money I save to an animal charity”… that kinda thing).
And, to paraphrase The gospel of Luke, since it IS Christmas time, let the rising sun come to you from heaven and shine light upon you and those around you living in darkness, and in the shadow of death, let your feet be guided in the path of peace.