I agree with everyone. 14 years is a great age for a lab. Mine lived to 15, but her last year or two were pretty tough The healthiest thing for you to do is trust you did the right thing. You can't doubt yourself or the vet right now because you can't take the decision back. You had only the best intentions for the dog, and I know he is in a better place with no pain now. Try to accept that he is resting in peace and you did the right thing.