Sorry for your loss. It's absolutely brutal.
I lost my Maso (English/Cane Corso) Mastiff in August. He was my fourth Mastiff and I told myself it would be the last one. After four months of being depressed, I drove to Ohio and got an American (English/Anatolian) Mastiff just before Christmas. He instantly cured my illness!
I must say, however, that Christmas puppies sound great until you realize all the extra work it entails around the already crazy holidays.
I agree with those who recommend the in-home euthanasia. It's so much better for the dog (and was for me), being surrounded by family and friends.
Mastiff personalities and traits mesh perfectly with my own, and their constant vigilance/protection is reassuring, particularly in the backcountry, where I spend lots of time. I'll never have another breed but the shorter lifespan is a bummer. My last two only made it 8 years, but they were great years, and I would do it all over again, like I am now.