It's perfectly normal to feel nervous when a beloved pet has to go under sedation for surgery, even when it's something very routine and low risk! The truth is all surgery has risk, and even though we're doing it because it's what we've determined to be best for our pet's health and happiness, it's really difficult to ignore that very valid worry. Especially when it's the first time that particular dog has ever been under (at least, it's always worse for me the first time!). I do feel bad about how loopy anesthesia makes them, because I can't explain why it was necessary. But dogs are brilliant at living in the moment, and he'll be recovered before you know it, not even really aware that much is different!
I feel guilty taking my dog to the vet sometimes just because he doesn't much appreciate what goes on there, but I know it's the best for him. It's okay to be nervous and feel a little bad about putting them through a bit of stress and pain. At the end of the day, though, you know you're dog won't be making puppies!