(“. . . balloon ascensions, flaming hoops of fire, and lions . . .”)
I have observed before that many riders lament how much better their horse goes at home. I try to persuade them to re-define “home” as that space created between their legs and the contact with the bit where the horse can feel confident and secure in his obedience.
I know people who coddle their horses by trying to avoid any possible distraction even in their own arena. If a car pulls into the driveway, they stop to let their horse look at it. If their horse is casting sideways glances at a jacket which has been tossed over a fence post, the offending object is immediately removed before any riding continues. You get the idea. The environment is sanitized of anything which could remotely influence the horse’s performance. There are exceptions of course—distractions that no normal horse with a brain and nerve endings should be expected to ignore. A short list would include balloon ascensions, your neighbor’s kids careening past on dirt bikes, flaming hoops of fire, and lions.
On the flipside a horse which is never been exposed will never acclimate to anything. That’s why we might drape a cooler over a pole your horse is jumping. That’s why Axel Steiner while prepping Costa Rican riders for the Pan Am games scattered a half dozen open umbrellas across the schooling area. That’s why you need to ride with four other horses in the ring occasionally and not always alone. Or with flags fluttering or whatever.
Be reasonable and be patient. You shouldn’t over face your horse with too much too soon, but to be successful your horse has to learn to take things “in stride.”