Oh, I am so sorry to hear about Sabre...
It does not matter how we lose them; quickly, suddenly, or when we KNOW they will be leaving us due to a prolonged illness, the loss of a true friend is not ever easy to take. I can't possibly imagine what you are going through, losing him that quickly. How old was Sabre? It almost sounds to me like a heart problem, and if that were the case, I would venture that his quick passing was nearly if not completely painless, and you can count that as a blessing. He didn't suffer the pain of enduring a cancer or other body-eating disease. I know that really does not make this any easier for you, though.
Try to remember that you gave Sabre all the love that you had, and that he knew how much you loved him. Remember that he was in your family and treated with the dignity that a true friend deserves. You gave him the life that is denied so many other dogs; the chance to be with the family that he loved and the ability to spend time with you as much as he wanted. You are good parents.
Rest easy, Sabre; you'll be missed, but your memories will forever be cherished.