I fully sympathise with you. A few years ago I had to have my dog put to sleep because of severe arthritis. At the time that was probaly the only time I cried for 30+ years and it lasted for a week or more. It was the absolute very worst appointment I made with the vet and even harder to go in knowing that I would come out without my buddy. It's only now that I'm thinking of getting a dog again.
What I missed the most was getting met at the door when I'd come home from work, visiting etc. He was "supposed" to be there for his pat and scratch under the chin. I used to talk to him and as well, they are always there for you and no complaining. My doctor told me that I missed him more than I realized especially his companion-ship.
I did up a poem, if that's what it can be called and I looke4d at dog sites just to do something to remember the good times and played with his toys for a while and gradually I was able to grieve for him and just remember he was always my best friend.
I will mourn the teenager I never was and strive to make that dot of light way out in the far reaches of the end of the tunnel turn into a bright sun.
WE ARE NOT VICTIMS. WE ARE THE SURVIVORS!!!