I got this question after my post about herd dynamics the other day...
"Gosh, what a great blog and especially this post; I'm a new horse owner and I think I've experienced my horse do this to me at various points in the last few months. Any suggestions on how to re-balance the hierarchy after mistakes have been made & the dynamic has been improperly set?"
My best answer to this question is, do groundwork. If you have a round-pen, start there. Get the horse moving and learn how to move the horse using your body. For example, if you move toward the horse's hip, he will move forward, away from you. If you move toward his shoulder, he will stop and/or turn. If your horse comes straight at you in an aggressive manner, he is totally not respecting you. You need to get him moving away from you then turning on your signal. If you have control over where his feet are going than you have the leadership role. Don't spend too long in the round-pen, two or three sessions are usually enough for most horses. After that, they start getting bored and frustrated. Once they are moving well off of your commands, put on a halter and lead and work on leading.
If you don't have a round-pen, work with a halter and lead rope. Practice leading. Even if you think your horse leads fairly well, they can usually do better. Expect your horse to follow at your shoulder and keep pace with you no matter how fast or slow you are moving. He ha to always respect your space. If he is crowding you, he is dominating you. In other words, the horse should always be aware of you and looking to you for guidance, for leadership.
Be especially careful at feeding times. If your horse is pawing at the gate, banging on the wall, pinning his ears, he is not respecting you. Never feed him when he is doing any of these things, wait until he is quiet, with ears up then give him his food. This doesn't take as long as you may think but, you have to be very consistent, especially with a new horse.
If any of this sounds like gibberish or seems overwhelming, you probably need some help. Find an instructor who is willing to teach you how to do groundwork not just riding. There are all sorts of good videos that cover this subject as well although nothin compares to working with the real thing. People like Buck Brannaman, Ray Hunt, Tom Dorrance, John Lyons, etc. all have training videos. If you choose to go this route, I would suggest that you pick just one for now. They all have similar methods but do vary some. If you try to cram all of them into your head at once, you are likely to get frozen by indecision when you most need to act. You can come back to the rest later, you will learn more from all of them that way.
The other suggestion I can offer is, watch horses. Watch what they do, how they move, how they interact. It is best if you can watch them while remaining unobserved yourself. Try to see them without any preconceptions or expectations. Watch them while they are being boring...sleeping, grazing, standing around with their lip hanging low. Watch them while they are playing and especially when they are arguing. Watch the interactions between the alpha horse and the subordinates. Ultimately, the horse is the best teacher you will find but, you have to accept what the horse is before you can teach him something new.
I don't know anything about you, your situation or your horse so it is impossible for me to offer much beyond this. You are welcome to contact me, if you have specific questions and you think I can help. Just send me an email. I hope this helps.