It might seem strange that by feeding food, we can improve food manners, but it's true! Actually we can eliminate biting.
We get more of what we reinforce. If you feed the muggy/pushy horse, you will get more of that behavior. If you reward your horse for keeping his head to himself, he very quickly will understand that standing relaxed is what will earn the reinforcement.
We call this an incompatible behavior. It's impossible for your horse to mug you AND simultaneously keep his head to himself.
When your horse is learning, it's important not to push him away or correct him in any way and the reason for this is that we don't want to interfere with the learning process. We don't want to give him the answer but let him figure out what is working. It can also be quite reinforcing when we engage with them in any way.
This is the first time this sweet mare has done R+ and you can see in a few short minutes she figured it out. If horses are this smart, just think of what else we can teach them when we are telling them YES for their correct decisions. Not only do we develop boldness and confidence, but we build heart and try. It's pretty special!