My trainer has a couple of cold-backed
horses down at her main barn. One mare in particular, Chloe, needs to be lunged until she is "warm" enough to get on. It's just better for her, because she can get used to the saddle and girth without the weight of the ride. It's also better for the rider, since they don't get their butt dumped in the sand.
A lot of the time, I find that hot or explosive horses (that aren't cold-backed) just need to be let go when you get on. Much of the time I see nervous riders lunging their horses for twenty minutes before they get on, then they struggle to get the horse to stand for mounting, and once on, they proceed to pull and yank on the reins when the horse tries to walk forward. The whole ride just ends up being a fight between WHEEEEE horsey and WOAH HANNIBAL rider.
Really, I had days with Freddy where he'd be feeling either fresh or spooky, and I'd simply let him go for a loose trot or canter, or even just a speedy walk. Afterwards he'd be ready to work, and I wouldn't spend the ride fighting with him about being calm and listening. I do the same thing with a couple of other horses, including my trainer's warmblood "ex-stallion", Booboo (I know, I know).
As for displays of exuberance (not pain!), you just have to be able to stick with it. Lunging isn't going to really fix anything, nor is fighting it and holding them back. I see riders in the warm-up rings at Spruce when they first get on, and sometimes the horses just take off bucking and kicking out of sheer excitement. Most riders just contently sit through it as if it's just another day.