I'm pretty determined not to ruin the progress I've made at Christmas, so I completely get where you're coming from. Blood glucose is one thing, some fasting and controlled days after will bring that back in line hopefully from what I've seen others say. However, I'm also trying to lose a lot of weight, so staying within my strict carb limit isn't the only priority, and it's not much good if I consume 84,312 calories worth of fat and protein!What a great idea for a thread!
There's just the two of us, and my husband cooks Christmas dinner, which we have in the evening as daylight is so short. He is a superstar! He makes the best roast potatoes in the world (I taught him how) but he doesn't make them! We have a roast rib of beef and loads of diabetic-friendly veg. with butter on. We only eat that course - no starters, no puds. I do have one glass of red wine. This year I will have a few nuts which he allocates me as in my mind there is no such thing as "a few". That's why I also don't have the two squares of dark chocolate which would be okay if I did, but the rest of the bar would be calling to me, so we don't buy it. I don't crave his chocolate/biscuits/cake/sweets/peanuts/crisps - am completely indifferent to them since starting keto. That was an unexpected and most welcome side-effect. I'm not goody-two-shoes - it just happened.
I'm not a snacker - I wasn't brought up that way - he is, so he snacks all day, but they are his snacks not mine. So they don't interest me. I'll brunch with something diabetic-friendly when I am hungry. We used to have hot chocolate with brandy after a long walk on the day, but I just have the brandy now, maybe with coffee with cream.
Leading up to the day we do some mild socialising so I do come across people who try to press me to eat/drink things that will do me no good. It annoys me because I see it as manipulative and inconsiderate, but I woz brung up proper so I just refuse politely but firmly, and the more they push (why DO people do this? It's to make themselves feel good. Tough.) the more polite I am. Passive aggressive I can do.
It's honestly no hardship for me to do Christmas this way, but I have no criticism whatever of others having a different approach. The important thing IMO is to stay as healthy as we can manage while having as good a time as we can safely manage. That's different for all of us.

As for those who encourage diabetics to eat things that are bad for them, it really annoys me too. However, on the couple of occasions I've had to deal with it so far, I've taken the line of "Are you really that incapable of enjoying food and alcohol on your own terms, that you need me to brighten your day/night by joining in? It's a bit weird, no?" Fairly successful in silencing them so far.