Anxiety Support Group
Anxiety is a physical condition marked by intense and persistent feelings of distress, fear, angst or dread. General anxiety caused by routine day-to-day stresses usually passes quickly and is experienced by almost everyone at one time or another. However, such feelings that linger over time and are very difficult to cope with, and which lack a clear cause, may indicate...

I'm in treatment, doing well, and working diligently to recover my balance ... and it is hard work. What helps is the journal I have from the beginning of treatment, and having a base to use to set up new choices.
Best wishes to feeling better.
Something like, "I would love to join you but find that holidays are very difficult for me. I'm going to spend the day hiking but I will be thinking of you all and will be there in spirit." They'll take it like they take it. I don't know your family but some of my family totally understood and others felt sad. Fewer were angry but they tend to be angry most of the time anyway so I don't think it had much to do with me.
Then make sure you have a plan for yourself to enjoy the holiday. That may be a Star Trek marathon with one or two friends. It may be just napping and soaking in the tub, reading or being out in nature.
On the other hand, if you want to go, you may ask others for the support you need or prepare them for how you'll handle things. You may need to step outside, just nibble at the meal and not eat much, have some quiet time to lay down in a guest room, etc.
Hope you find the answers that work for you.