I've had dogs all my life - mostly from rescue centres - you know - the ones that people kick out in the new year when they realise that the "cute little puppy" needs more than they're prepared to give.
I've experienced their passing, as Dan has - it never gets easier and I'll never get used to it. To me, and I guess to a lot of other folk too, a dog is more than an animal - they're a companion, a friend, maybe a best friend.
One piece of advice I was given which I found worked for me was, on losing a dog, to find another as soon as possible. Not to compare, not to help "forget" the dog who's gone, but to give hope and comfort to, especially after a bad start in life. To make a new friend - not forget the old ones.
I'll never forget any of the dogs I've been priviledged to offer a home to - they're alive in my memories, and always will be.