My grandmother passed away last year, and she was the first of my 4 grandparents to go. Yes, I am lucky to have them live so long, but having her go first just made it harder to deal with.
Her birthday was 29th of september which is the day after mine, so we used to all get together then. Birthdays are now hard to handle for me, as is Christmas.
But she's no longer in pain
Sorry to hear of your loss, trust me it gets easier with time.