We can't expect ..."that people are going to show up and things are going to be different, that people are going to behave differently in our family than they do the 11 other months of the year. Your mother or father or sister ... aren't going to change just because of the holidays."
I recommend that you:
Have a plan and be proactive. Do not be reactive. Find some innocuous phrases and a few direct ones. If you have to, practice in front of mirror a dozen times. Strategize ways to get a break and get away periodically. Try to get enough sleep, eat some healthy meals, and get a bit of exercise.