Based on what most of you describe, I think you are riding my horse! :winkgrin: It is actually great to hear that he is not the only one. Everything he does is what all horses do … it’s HOW he does it, it’s on springs and jet rocket boosters, and it doesn’t seem to have an off switch that either one of us can operate.
One of the best instructors I’ve worked with, the only one who really ‘got’ what was going on with this horse, said she thought that he is very easily and quickly overwhelmed, and then his adrenaline spikes and doesn’t come down.
I asked the local vet hospital if they could take out about half of his adrenaline. They said that’s not on their list of treatments. 
A little research didn’t turn up much help on horses or people with more adrenaline than they need, other than to use it up with exercise. My horse is most rational and does go best when he is on full eventing conditioning program - # of rides per week, trot sets, gallop sets, whole deal, so I do think my instructor’s adrenaline observation is likely valid.
I also think the comment of ccr0009 / Allison S “It’s not about acclimating them to different things, but instead, make it about following rider’s instructions.” is right on.
On a given ride, I can repetition-condition to quit spooking every time we pass Identical Clone Jump Standard #28 in the ring, or even move/remove #28 … and he will start spooking at something else. It isn’t the thing, it’s the spook that he is after.
So yes, it is about paying attention to the rider No Matter What. That’s tough because horse brain tends to disconnect-on-spook, but that’s what we work on. Caveat that natural hardwiring to disconnect-on-spook means this work is a bowl that is never full.
And the futility of de-sensitizing is also a disconnect with the traditional input from instructors & clinicians who don’t yet know this horse. They want to desensitize Identical Clone Jump Standard #28. I have to explain that he’ll just transfer the energy to spooking elsewhere. The good clinicians do remember Sir Spooksalot’s behavior when they see him at the next clinic a year later!
There is another bit of behavioral fallout re instructors. For about half the years I’ve had this horse I was not in a trainer barn, and so I’ve worked with a small list of trainers/clinicians. Well, once each of these instructors has his number, he/she AVOIDS getting on my horse. They get on other horses for a few moments to demonstrate or fix … but not Spooks, although heaven knows there is a lot to fix. I think they know that that This Horse will make them look like an idiot in just a 2-3 minute ride. It takes longer to get his attention and establish the boundaries. Anyone else run into instructors reluctant to demo-ride your spooky/looky horse?
One of the few exceptions was Gina Miles in a clinic the year after she won Olympic Silver, and I salute her for getting on a difficult horse when the rider really needed the help to understand. My horse has the honor and distinction of having come this close to dumping Olympic Silver Medalist Gina Miles in a Beginner Novice clinic.
I could see her shocked expression as she was swinging out in space beside him after he pulled a Level 10 Spook-Evasion at a jump standard! Great save by Gina! :lol: She got him going, though, and declared he was a lot of fun through a 5-jump gymnastic and took him through a couple of extra trips with smiles from her and him both. My hat is off to every instructor who will voluntarily demo-ride Sir Spooksalot! :winkgrin: :yes: :lol: