"With a good relationship comes good control, and with good control comes safety. Also you want the horse to want to be with you and enjoy whatever you are doing together. To achive this you have to let the horse make choices and think for himsel, and not be forced or punished for mistakes.
The horse needs to know that you are his friend and that you are there for him to help and guide him.
To get good control you have to start communicate with the horse from the ground. You need to be the bigger horse that tells the other what to do and how to act. Like being a parent for your kids. You want to be the kid's friend, but you also have to be in charge, if not the kids would probably go crazy.
You need to know that you can trust your horse, so if you tell him to do something, you can be sure that the horse will actually do it. Like for example telling the horse to move out of the way if a car is coming, or going into a horse trailer, or being able to stop if you see something in your way when you are out riding. You need to know that the horse will listen, in any situation.
I am sure you wouldn't want to drive a car you couldn't stop, stear, speed, break, back up or park. Well I wouldn't ride a horse I couldn't stop, stear, speed, break, back up or park. Being able to do all these things is your security.