I myself have a dog whose time is approaching, too. I understand your pain. He's a sweet old fart (91 in dog-years), who spends his time sleeping, eating, and well, farting. Since I am an atheist, I think there is nothing on the other side - no pain, no illness, no conscience, nothing. Just know that your beloved companion will be going somewhere where they can never be injured or fall sick again. It takes time to get over the loss of someone close to you, but, as ~Faolan~ said, you do move on eventually.