In reference to the OP,
I got a golden retriever from a fat girl down the street when I was 17, he was your typical city golden retriever, bandana wearing ,chasing Frisbees and tennis balls at 1.5 years old. I picked up a copy of water dog in January and wore the pages out as well as him 2 hours a day on a lake , by the next duck season I had what would be called a finished dog, hand and whistle commands , no e-collar would cast out several hundred yards to find a bird, he would drop one retrieve and go to another on hand and whistle commands, fast forward a few years,
I’m in school in Colorado, and have to move from one Apt to another that won’t let me have a dog, ask a friend if he can board him for the summer till I get a new place, he says sure, he is on the other side of town so I only get to see the dog once a week and try to work him when I can, well Duck season rolls around, I have a new place, I pick up the dog and he is wearing a bandana and has a tennis ball in his mouth? The guys girl friend is trying to tell me to bring him back after the hunt season? In like a week right? (NOT)
I work him for a few days trying to brush off the rust, he does ok and I think once in the field he will snap to it. His first retrieve he takes the duck to the other side of the pond and starts to eat it and won’t respond to commands. He gets a good AZZ kicking and I figure it will work out, he works only ok the rest of the day, didn't have his heart in it. next hunt 3 days later we run into some other hunters and he wants to follow their dog and play like he was in the park , I was embarrassed, called my friend and told him to come pick up the dog if he wants him, being still in school I had no time to retrain the dog and he might as well keep it. In 4 months he and his girlfriend had ruined the dog.
So I would say what your friends/family do when you’re not around can affect your dog’s performance.