I went to our office Christmas party when I was just over three months sober, thinking I was obligated to go. I was very uncomfortable, which I would have masked before by drinking. I didn't. I ate, got my five-year pin, and got the heck out of there.
Haven't been to one since.
Christmas parties are not manditory. Don't jeopardize your sobriety out of some sense of obligation. Work certainly won't be there to pick you up when you fall.