sj257 - I suffer from anxiety too, and I have found that making lists really helps - I make an overal,list of the things at need doing - presents, cards, dinner, decorating the house - and then I break these down into the individual,parts - e.g. cards is broken down into buy cards, buy stamps, do address labels, write cards, post cards.
Then I look to see what I can do in advance - I make breadcrumbs, stock for gravy, apple sauce etc, and peel the chestnuts, and freeze those, so there is less work to do on the day.and freeze them. Over the years I have realised that we really don't need a starter, so I don't bother with that. I used to make a home made Christmas pudding, but hardly any of it got eaten, so now I buy one.
In December, I look to knock off big jobs nice and early - buying, wrapping and posting presents, wrapping the stocking presents, writing the cards - knowing I have ticked off some big things on the list really reduces my stress levels. And spreading them out makes them less hard work.
This year I have put the whole,thing on the computer, so all my lists will,be there ready for next year.
Over the years I have worked out what matters and what doesn't, and I only do the things that matter - and no-one has ever complained - Christmas is still a special day.
It also helps to remember that Christmas dinner is just a roast dinner - that makes it less worrying, in my mind.
Try not to worry too much - and come here and vent, if it would help.