Hello everybody - thought I'd join the thread and add my twopenn'orth. Just had first Christmas since DH left at the end of January and moved into a flat with OW (work colleague 26 years his junior) in middle of February. They got together physically after their work Christmas party in 2015, but it sounds like an emotional affair had been going on for a bit before that. Long and complicated story and if anybody needs something to help with insomnia, then all the gory details are in my original thread at www.mumsnet.com/Talk/relationships/2560619-Please-help-Husband-leaving-after-26-years?msgid=63554400
I've found it both easier and harder than I thought. The DC were all at home yesterday and we had a lovely day. They have part-time jobs now and I got some lovely presents from them all. The DDs shopped for and bought the ingredients for the Christmas dinner and DD1 cooked it. We all lazed around, did things as and when we saw fit, played Monopoly, bickered over rents on Park Lane and chilled. It was nice not to have an atmosphere; STBXH always drank a lot at Christmas and we were all a bit nervous of how his mood might go. He quite often seemed to sense this and it could make him very "touchy". His moods could range from a sort of forced bonhomie, to maudlin and sentimental to bitter, self-pitying and critical. I didn't drink much at Christmas at all because I found it made me feel vulnerable - don't know why.
This year the DC are all of an age to drink and we had quite a lot of booze throughout the day, but nobody was drunk and it was all very relaxed and good fun.
STBXH used to charge around the place demanding that mess be cleared up straight away before anything else happened and that presents be stacked away upstairs so the house didn't "look like a shithole". Nothing wrong with clean and tidy, but it was the way he went about it that made it a less than relaxing experience. This year, we just pottered around and picked things up as and when. Some things are still waiting to be picked up. We ate dinner when it was ready and DD1 wore her onesie with the hood up and the cracker hat perched on top; DD2 was still in her pyjamas 
Nobody gave a monkey's!
Despite all this, I still found it very hard and cried quite a few times. I think it was thinking about times gone by and not just with STBXH, but also with my parents (both died over the last couple of years) and my brothers and the good times we had together. Christmas seems to underline the things that have gone wrong and the people who are no longer here: "love and happiness all around" is quite difficult to take. I felt sorry for the DC who were having a Christmas that was so different from last year (before the bombshell dropped) and who have all had a very difficult time of it.
I also found it very hurtful that there was no card or anything from MIL and SIL. I think they may well have sent things for the DC via STBXH, but nothing to the house - almost as if they didn't want to risk me being on the receiving end of any good wishes. I always organised the presents for his family in the past; the only thing I got STBXH to do was write the Christmas card, which I bought, stamped and posted! This year I wasn't sure what to do, so I just arranged for Christmas flowers to be sent from the DC - as I did every year - and we all signed the Christmas cards. Then I fretted over whether that was the right thing to do or not. I feel like a leper - I have been cut off completely by them since STBXH left. They all live a long way away and I have no idea what he has told them about the split, but it's so hurtful to be ignored and cold-shouldered like that. As if I had committed some great crime.
DD1 and DS are both working today and I planned to take DD2 out for coffee and cake for a surprise. However, she told me she was being picked up by STBXH at midday to go out for lunch and I just got so upset. I feel very guilty now because I didn't want to make her feel bad and I do acknowledge her right to see her dad, but I suddenly felt quite bereft and got a foretaste of things to come when all the DC move out and I'll be all on my own. Self-pity fest! DD1 and DS don't see STBXH out of choice due to their previous relationship with him and also the way that he left. DD2 sees him a couple of times a week - refuses to meet OW - but it's hard because there is now an unspoken rift in the family which makes things awkward for me and the DC, but was not caused by any of us. I make a huge effort never to say anything about STBXH and OW or badmouth them, but sometimes I can't help getting upset. I think it's the fact that I'm feeling sorry for myself because I'm sitting on my own on Boxing Day, whereas he will never be on his own because he has OW. I feel guilty for making DD2 feel awkward; then angry because it's not me who has put us in that position; then sorry for myself because it's supposed to be all love and goodwill; then sad because of memories of Christmas in the past, then scared because I don't know what Christmas in the future will look like and where I will be living. And so on ....
All in all, a bit of a mixed bag this Christmas. However, as so many posters have said, it is just one day and it soon passes. I think the best way to cope with any "alone time" is to use it to catch up on things, or have a bit of a relax and pamper session and try not to see it as something negative. I find it really helps not to bottle up my feelings and if I need to have a good cry and a rant and kick Christmas baubles up and down the stairs and assault the Christmas tree angel (bought many years ago by STBXH!), then it's good to do it when the house is empty and the DC can't hear. I have been taking it out on the poor tree angel - on Christmas Eve I pulled her hair and her halo fell off. Maybe it's subconsciously what I'd like to do to STBXH, except he has neither halo nor hair.
Love to you all out there who are going through this. All different stages and circumstances, but it's still difficult for us. I think what keeps me going is accepting that it's perfectly OK to cry, howl, rant, have meltdowns and feel down, as long as you can get back up again afterwards.
And, as usual, I have managed to turn what was meant to be a short, succinct post into a drama llama novel ... well done if you made it to the end 