So sorry on your loss Greg.
I lost my mum at 84 week before Christmas 2014, came completely out of the blue. Mum lived with me and I looked after her in between work. Strangely enough the day she fell ilI I took the day off work to cook her nice meal and to just have a nice day with her. 5 days later mum passed away. Although she was my mum she was also my best friend in life and I found it very hard to accept the loss at first to the point I convinced myself she had just gone on holiday and would be back. I didn't allow myself to grieve and kept busy, something when looking back I regret now as it was almost like denial and the guilt feeling of not bereaving overtook me. I felt almost selfish. It wasn't until some 8 months later the grief overwhelmed me. The key is to talk to friends and family and share your feelings, I did go to see a bereavement councillor which helped enormously who taught me it's normal to feel the way I did, it can take time to come to terms with a loss, in many ways there is no time limit for grieving. I focus on my happy memories of these days and accept she is in a happy place but also she is still there in my life. End of the day I know she would want me to be happy.
Christmas time is still very hard but it does get better with time. For me personally I keep some of my mum's favourite things together in one place with photos and when I have times I wished she was around they provide some comfort, it's just my way staying close to her.
All the best to you,
Tim.