Every pet we have leaves its mark on us because they make us better caretakers of the pets that follow. I've learned how to be a better pet mom from all our dogs and cats who have been a part of my life.
I've been there too many times too. Take consolation that you made the decision a pet needs us to make: to end the pain and suffering in a humane, caring, loving manner. They can't do that for themselves.
The fact that you were there with him at the end and could hold him and love him until he passed is a much better scenario than having him die one day while you're at work, or something. Believe me, I know.
I'm sure that you are a GREAT pet dad and Bop could not have had a better life with anyone else. He was as lucky to have you as you were to have him.