You have taught him that you'll follow him anywhere, everywhere, even if it seems like nowhere, whether you want to or not.
If your dog is pulling so you take his collar in hand and hold him close to you, practically lifting his front paws off the ground while you're walking and explaining to him that if he doesn't stop pulling he will hurt himself, what have you taught him?
Not one single thing that is good. No, your dog does not understand you or your actions no matter how many ways you try to explain it.
If your dog is on leash and pulling you to get to anywhere, everywhere, even if it seems like nowhere, and you stop, only to continue the forward motion once the leash is slack, what have you taught him?
You have taught him that he can only get anywhere when the leash is slack. Yes, it is easier said than done, but when you take the time, be patient and be consistent, it's worth it. We want the leash to be the safety net, not the controller. When we use it to pull our dogs or allow ourselves to be pulled, it's not an enjoyable walk for either of us.
If you're out for a walk, and your dog is walking nicely next to you so you slip him a treat, what have you taught him?
You have taught him that being next to you is a good place to be and the more it is reinforced (i.e. treated) the stronger the desired behavior will be. In other words, your dog will want to be by your side.
If you yell at your dog as he pees or poops in the house, what have you taught him?
You have taught him that it is SCARY to pee or poop in front of you because you yell. Then he may stop peeing or pooping in front of you anywhere. Inside or outside. Instead he may hide where he goes when he's inside, and never want to 'go' when he's out with you.
If you come home only to discover that sometime earlier your dog had peed, pooped, or done something else to upset you, and you yell at him, what have you taught him?
You have taught your dog to be scared of you when you come home. Your dog will have no idea why you're yelling at him. And that 'guilty' look? That's just worry or fear. Again, it may not be the lesson he learns the first time, but then again, it might.
If your dog poops in the house and you "bring" him over to it, pick up the poop, bring him and it outside, drop the poop then give your dog a treat, what have you taught him?
Lets try to break this down a little.
Your dog poops in the house and you "bring" him over to it, what have you taught him? Most likely you have taught him to be to be very concerned when you come to him with 'that look' that you know is on your face, scared of you when you reach for his collar, and definitely to NOT want to come with you.
Then you pick up his poop, bring him and it outside, drop the poop and give him a treat. Huh? That just doesn't make any sense. Do you think that the treat at the end would be telling your dog that if he poops outside, he'll get a treat? The plain and simple answer is, no. Being with your dog and giving him a treat right after he poops in the yard is what tells him that.
The true scenario above happened with an older puppy that had not had an accident in the house in a while. It is quite probable that the dog was giving his humans signs that he needed to go and they weren't paying attention. When you gotta go, you gotta go.
All of the preceding scenarios can be prevented or taught with management, training or both. If you need assistance with any of them, please find a positive trainer to work with who can guide you and your dog down a path that will help you build a long lasting and trusting relationship.
Before you act or react, THINK "What am I teaching my dog?"