Sorry to hear this OP. I feel for you, really I do. I had my 11.5 year old Lab put to sleep last month. Hardest thing I have ever done. I was there till the end. I lay on the floor spooning him, his head on my arm, stroking his face, ears, neck whispering to him all the good times we had on his days out, playing tug in the garden, telling him how worried I was when he went in the sea with big waves after a yellow tennis ball I chucked in too far. Couldn't see him for ages because of the waves. He was out there for 10 minutes at least. Then out of a wave he came, ball in mouth, had a shake, dropped the ball, wagged his tail, and wanted to go back in. That was a heart stopping moment. The vet and I laughed when I told Louis (my dog) this, he was gone by then but I had to tell him how much he worried me.
After 30 seconds or so he was heavy and he was a rest.
The vets is round the corner from my house and I walk past everyday at least 4 times. I always look at the building and picture him in the room with me. I know people say don't get another dog for a while but to be honest, I wanted one only a week after. I miss him but I miss the companionship more. The excitement when they see you, the dog hairs, drool, water all over the floor next to his bowl. When I cleaned up the last of the poo in the garden that was a hard time. Silly I know. It was only last week I think I have got all the dog hairs up. I clean every day and hoover 4 times a week.
My biggest regret was not asking the vet to shave a bit of his hair off. I wanted a tuft to keep. That upsets me. Collecting it from around the house isnt the same.
Sorry for you loss OP and to others who have recently lost loved a one.
We don't deserve dogs.