Is there anything a horse cannot be trained to do? (This question, of course, takes into account physical capabilities.)
I don't mean "Can you train a horse to stand on its head," I'm asking if there's anything that when a horse outright refuses to do, will remain refused for the entirety of its life. Like a horse that has never been able to cross a river its whole life being taught to cross a river, or a horse that refused to ever jump learning to accept jumping. (Assuming they don't have some physical reason for not wanting to, and its just a mental block.)
I ask because I've heard both "Oh she can NEVER cross water!" from trainers and different trainers say "We've been working on crossing water (over the course of many years,) but she still refuses to," and I really can't figure out what is "right." Is it right to just give up and accept that your horse won't? Or is it possible that every horse can be trained to do anything they can physically do given time and consistency?
No particular reason for this question, just wondering on opinions.