...The moral of this story is that if we don't react to a spooky stimulus, don't even look at it, then the horse will pick up on this and, so long as you are viewed as the leader, they are far less likely to react to it...
Hate to break it to you, but I almost never know what my horse spooks over. Usually we land about 6-8 feet to one side without warning. Or she'll be trotting happily, and then do the OMG Crouch.
If she does look in advance, it is much easier to deal with. If there is something she alerts on, then we can deal with it together. And at times like that, with Mia - not with all horses, but with Mia at least - it works best to let her look at it, let me look at it, and then about 5 seconds later let her know what I
want to do about it. And if it is a rattlesnake, I thank her and tell her what a wonderful horse she is as we go somewhere else.
Further, some of this "leader" stuff is overblown. Frankly, a well trained horse should be able to go on a trail ride without first needing months of introduction to and working with an individual rider. Some horses may be too high-strung to get there. That is a fault in their temperament. Mia is a sweet horse in some ways, but her temperament is a fault, and the work we are doing is intended to overcome that fault to the maximum possible.
But if she was inclined to walk into trees unless I steered her around them, I'd get rid of her.
And if someone wanted to "fine me", I'd strap my 44 to my side before mounting...
Focusing on something should NOT frighten a horse. It would be pretty tough to work on a ranch if the horse spooked when the cowboy wasn't looking at the horizon. I need to be free to look at something in the desert when I ride without my horse deciding that means to walk into it or to spook over it. Don't do ranch work, but I ought to be able to watch what a car or dirt bike is doing, or watch for a rocky spot or stare into a wash without having my horse freak over it. And she doesn't. She may spook sometimes, but far less than she used to and she never does it because I'm focusing on something.