Have you changed your holiday traditions?

I grew up having Christmas traditions that involved having a Christmas tree, lots of presents under the tree December 25th morning and then a family dinner on Christmas day. We had family get togethers over the holiday, regular large outdoor parties where Santa Claus visited and brought presents for all of the kids and even gifts for the adults. My parents spent many hours decorating the yard, house interior and exterior. Christmas was a time of celebration, gift giving, decoration and family time together. We rarely went to church at Christmas and didn't focus on the Christianity part of it generally speaking though some years when I was younger we did. Now I'm an adult who no longer lives with his parents. I have a girlfriend who lives with me but she's from another country that doesn't celebrate Christmas. I'm an atheist and prefer to type Xmas without Christ in it. Even though I've sometimes put up a tree as an adult I'm not so sure I want to keep doing it. I've reached a crossroads and it's time I started to develop my own traditions but the problem is I'm not sure what to do. I guess I could start by writing a list of what I value, what I enjoyed in my life and morph that into some kind of new tradition but it's easier said than done. For a while I simply went on holidays to California and thereby bypassed the need to put up a xmas tree or decorations. I don't have kids which makes it even more challenging because Xmas was always largely about the kids and giving them gifts. Christmas was a huge thing for my mother and now that's she's no longer alive and I live on my own, I'm experiencing somewhat of an existential crisis.

Has anyone dealt with a similar thing and what have you done about it?