Not everybody is sensitive to anniversaries, but when you are, it can be exquisitely painful - it's as though a body clock alarm is going off, and what happened at this time (last year, five years ago) is felt again. I am so sorry for your loss, but you gave her everything in human power - care, understanding, respite from pain, and loving arms for the journey. One day that will be more comfort than it is now. Seen from the outside, I still think what I thought when I heard she was gone: that if I go as she did, I will have all (except more time, sadly not in our gift yet) that anyone could ask for.
There is an evening prayer in the Episcopal prayer book that says it better than I can:
O Lord, support us all the day long, until the shadows lengthen and the evening comes, and the busy world is hushed, and the fever of life is over, and our work is done. Then in Thy mercy, grant us a safe lodging, and a holy rest, and peace at the last.