Life is never about its last days, or the end, but the content of its whole. If your dog enjoyed its lifetime with a loving family, then the end only exists to highlight the joys and wonders experienced during life, and to truly cement the uniqueness and beauty that life is.
John Keats' poetry is an outstanding example of a way to see death as less of a tyrant, and more of a enabler for all life. If you haven't given some of his works a good hard read, I recommend that you do.
That being said, enjoy your dog's company just as you have for every other day of its life, and nothing will have been lost. That's what life is all about.