I feel for you so much! It's one of my worst nightmares (other than anything happening to my DS). My mum is the closest person to me and I just can't even bear the thought of it and know full well I'll have to go through it one day. I cannot even contemplate your pain.
My brother died in January this year (last year now actually). On my birthday of all days! He was just 28 and totally unexpected - he ended up with severe pneumonia from the flu which we all had, so we're having to go through all the firsts with christmas / new year this time round.
We've just been through the first Christmas without him which was tinged with a lot of sadness all round as he was always a part of the christmas celebrations. New Years Eve was particularly hard as we remember he phoned my mum this time last year saying how ill he felt and we all just assumed 'man flu' as he was always, and I mean always going on about his ailments (he had an ingrowing toenail and asked if he was going to die!). But now we're having to live with the nightmare of guilt at having not taken him seriously. Next week we'll be remembering him going into hospital - not something we've forgotton but it's just highlighted more, if that makes sense then a week later the first anniversary of his death.
It's not easy, by any means. I know the pain I feel over this would be a million times worse if it was my mum - the same as this is my mums worst nightmare at having lost a child.
The death of someone close is certainly not something you'll ever forget and I'm sure the sadness never goes entirely. But you do learn to cope, somehow and have it more as a side thought, tinged with sadness rather than it taking over your entire life.
Love to everyone who is struggling at this time of year, and of course at times in between.