there's a few things about the holidays that could be the cause. It's normal. I remember reading about it and stuff even.

Holidays mark time. You can see that a year has passed, you still/now are thinking about what has happened in this time and

Either you're alone for the holidays (automatic ) or you're with people. sometimes those people are the family, people who may love you but you don't feel close too

sometimes there's pressure to "be happy" because everyone around you is... but you're just not then you are upset cuz you're sad, worried your bringing everyone else down and

I'm sorry this is a rough time, it's not wrong to feel this way though