Since Sonny is sooo sensitive I have to be totally cautious on what I do or don't do. I now have to do half of the riding with me teaching him stuff, prefecting things (like neckreining, bending, backingup, etc), or random patterns....than the other half I do a "passanger" lesson. He can go whatever pace he wants (within reason lol) and whereever he wants in the arena was long as he at least keeps walking.
I personally don't think it's right for someone to lunge the crap out of a horse to make them "sane". If you think of it in the horse's prospective...some person who you "thought" you could trust is either (a) chasing you with a crop/whip (b) making loud, scary noises. Unless done perfectly it can and will frighten a horse (unless the horse is realllly used to it).
I think it more makes their mind go every which way, and causes confusion in them.
I used to lunge Sonny all the time before I rode him, and when I did lunge him he tended to be spookier, and headstrong.....but when I stopped, he listened better and didn't spook as much
And I agree with Scout....a horse should not be in a stall