Have you ever read about adrenaline curves? Its not just busy, its physical activity thats needed. The anxiety adrenaline needs to be worked off and this occurs very slowly if you're sitting, quite slowly if you're just normal active but if you can build up a sweat by the activity it releases quickly.
Its a vicious circle if you're tired and stressed you're more prone to becoming anxious and if anxious its harder to get a good nights sleep.
DH appears a happy go lucky laid back person to outsiders. People say everything is water of a ducks back for him, but it couldn't be further from the truth. He appears to not stress about anything and then the built up not discussed stress from everyday life all spectacularly manifests around a (non) health issue.
DH did this mindfulness course which helped, slowly, to identify those things effecting him around him that he'd always thought didn't bother him. He's learning to say no more to people and to answer back a little. Its like a pressure relief that helps to take the edge off building anxiety.
Possibly for you Christmas at yours, suggests its not just your normal household but extra family/ friends? Are there some tasks that actually could be shared, drop off the bottom of the list because they're just not important enough?
We've got three DC. High as bloomin kites, very excited about Christmas. we're shattered from the long term at school and from working on the house garden every spare minute since moving in in the summer. Fortunately we don't have Christmas at ours this year and the stress relief is amazing. I love hosting it but for once its a stress I could do without.
Its not an easy journey but for DH after twenty years of being crippled he's completely turned it around the last two. He's done several courses of therapy CBT and mindfulness and had psychiatric nurse support but he really is much much better.
Have you ever managed to discuss the actual anxiety, not health symptoms from it, in detail with the GP or just been fobbed off with drugs?