Hi Lisa - so sorry you are struggling. I think you shouldn't fight taking your meds before your drive. You should be with family during the holidays. This is not the day to avoid taking your meds. Take your meds, get out of the car every 10 mins like Harry suggested, breathe, listen to nice music. Stop and call a supportive friend (arrange this ahead of time) and go have a nice time. you deserve it!
Motherly, you are doing great. My goodness, you've done so much already in preparation for this dinner. Your anxiety is brought on by stress. Tell yourself that you are going to have a beautiful day and then it will be over and you can relax. Sometimes knowing that the stress is "temporary" is helpful. Don't forget to breathe and why not go take a bubble bath before the big day?
"You don't find out that God is all you've got until God is all you've got."
"The mighty oak tree was once a little nut that held its ground."
"You are richer today if you have laughed, given or forgiven."