OK. I think I have a feel for what you are going through, at least as best I can sitting at a desk reading from a computer screen. Sorry if this gets a bit long, I’ll do it in two parts.
With anything you do with horses they will see straight through you if you put on an act. So, let’s think about Parelli’s lateral lunging (now it starts well before you start lunging them but that’s OK, this should demonstrate the point) and gaining respect/horse’s confidence through that.
Now, going back to what I was talking about your horse reading your body language. If, while you are lunging your horse, you don’t feel confident about it, or you are worried the horse will spook at something, or whatever, if you feel reservations about what you and the horse are doing, no amount of lunging will straighten out the problem. The actual lunging is only half the equation, the other half is how you deliver it. So you could have the details of lateral lunging 100%, but if your delivery of that is not confident, you won’t get anywhere.
So, let’s say you want to lunge your horse through a gate out of the paddock. As you begin the procedure you first say something like “off you go horse” (in lunging language of course, not English). If while you do that you have any feelings of trepidation at how the horse might shy from the gate, or seize up or get scared, the horse will see it and think there’s something to be scared of; in this case it’s YOU scaring the horse, not the gate.
So, when you ask the horse to do something you have to be confident that everything is OK. The horse might balk at the gate, it might be scared etc, hell, it might literally sh@# its self but YOU need to be calm and confident and persistently tell the horse, in language it understands: so having a quiet calm, but appropriately firm and persistent, demeanour that everything will be all right. Start with setting the situation so the horse SHOULD do what you want, then ask the horse to do what you want, then tell the horse to do what you want, and finally, if you need to get that far, MAKE the horse do what you want; the whole time, calmly, not aggressive or threatening, and WITH CONFIDENCE.
For example, one of the three bigger fillies I had been working on before I went overseas for a year and a bit, she was really touchy sometimes, she needed a bit more patience and so on, and needed to see confidence in me too. I take these horses out and lunge them around the paddock, I run about with them and get them jumping logs, or jumping gullies, or going in and out of creeks and so on. It helps them, and I could stand to lose some weight so it benefits both of us.
To get her out to the paddock I had to get her across a creek of fairly fast shallow running water about a food deep. I wanted her to jump the creek and I’d come over on rocks so I didn’t get wet feet. We got to the creek and it was the scariest thing she had seen, apparently. I asked her to have a look at it, she did, then I said to her “of you go, jump over there”, she wouldn’t go, so I said a bit louder, “off you go” (again, I wasn’t “saying” this to her I was talking through body language etc). She still didn’t want to go. I asked again, she could see that I wasn’t getting agitated, I was still calm as I was before, only she was getting agitated; she settled down a bit and had a go at it; but stopped short. I gave her a break, because she had a pretty good go at it, and eventually asked again, again very calmly; eventually she sailed over the creek. It wasn’t smooth and looked pretty messy to say the least, but she got there. I got across, and still got wet feet in the end. After about 15/20 minutes of playing about, I brought her back across and she crossed it like she had done it a million times.
When I initially got her to the creek, she was a little worried about it, had I been worried about her, or a bit nervous about what she might do, she would have cottoned on to that straight away and that would have told her “well there must be something to be afraid of”. But, over the years I have learned to stay calm; and horses can sense it easily.
So in terms of your thinking, and the way you behave, around a horse it has to be calm and confident, if your horse shies at a gate or a stick or its shadow, just ignore it, don’t worry about it, calmly look at your horse and say something like, “What? You see something? I didn’t notice” (say this in English, out loud, this bit is there to help you stay relaxed, not the horse) and remain calm and continue like nothing ever happened.