Be who you are. Take care of yourself.
If you do not wish to say yes for someone else's Christmas, then what would
you rather be doing? Is there room for any compromise? I have had the
experience of being caught up in someone else's Christmas too, didn't like it,
but didn't know how to get out of it (anyway that is almost over, but I
realize how I feel that someone else's sense of Christmas doesn't fit with my
sense of it).