My daughter and I took my Mom's dog to the vet a couple of weeks ago......same thing. Laura held her as the vet gave her the first shot and she almost left us then. It was comforting knowing she would be in no more pain. My Mom was so reluctant to let her go, so the poor thing suffered the last few months.
I am like Hanna. My husband has always taken our pets. The last pet we lost was 18 and we had gotten a new puppy three months earlier, so losing our old friend was not as hard because we had a new friend.
One thing about it........the way you described your pet shows you are a genuine, loving guy.