Had to do it for my 14 y/o cat. I understand how you feel.
Do what I did for my Sampson: Pat his head, tell him he is a good dog, and then tell him it is okay for him to go.
This is tearing my heart out because I’m reliving it with you, but you can’t put your emotional needs before his welfare. It is about what is best for him, not you.
Tears falling down my face. . .
Sad situation....Had to put my Ozzy cat down due to diabetes problems, he was 17 years and 4 months...