It isn't Christmas if the tree isn't up and decorated.
We tried to skip it last year because we went away for the week after Thanksgiving, which is when I usually decorate the house. By the time we got back to town, it seemed so late, like we'd get it up and it'd be Christmas so soon after and then I'd just have to take it right back down. But it turns out it was depressing to not have it up. It didn't feel like Christmas at all. We were broke, my job wasn't going well, etc. etc. But the minute we finally got the tree up, things started to look up.
And that's the point. The tree isn't for other people to see. It isn't intended to impress anyone. It doesn't have to be fancy, but it's okay if it is. All it needs are some lights. It's your own personal beacon of hope in a world that can sometimes feel really dark.