I hear you loud and clear OP, and others who found getting ready for Christmas a challenge. I hope you managed to have a nice Christmas Day despite things being difficult.
I have struggled with so many aspects of Christmas for years. Since being diagnosed I now realise that my ADHD traits make preparing and executing Christmas a massive uphill challenge.
I was diagnosed just over a year ago and since then I have had a bit of adhd coaching, read a couple of books (TBH I read the interesting bits, skimmed other bits, and didn't finish them but hey ho), listened to some podcasts and joined an online support group.
None of this has 'fixed' me. In fact it has made me realise that I can't be fixed because I'm not broken as such. But it has really helped me to understand why I struggle- as in which parts of my adhd create which difficulties.
With understanding has come more self compassion, which in turn has helped me to cope a lot better.
I have also learned a lot of coping strategies. As I said above, these haven't fixed me but they have made things easier. I guess I have more 'tools in my toolkit' and these tools are more suited to me and my brain than to a NT person.
Of course, I don't necessarily open my toolkit when I 'should'- this year I still procrastinated, ruminated, dreamt up elaborate awesome Christmas plans that never materialised, experienced sensory overload etc etc.. BUT it was a great deal less harrowing than other years, I was more organised, and more forgiving of myself.
Apologies if I am preaching to the concerted here, or if my post reads like a stealth boast- that wasn't my intention. I just wanted to say that there is hope that things can be a little easier, and that for me a lot of that came from understanding and being kinder to myself.