At what point do you quit trying with your horse? When do you say “Enough! He needs to stay at Second Level forever!”
BILL— A built-in limitation is part of the natural way of things—whether in humans or horses. Though it seems unlikely when you’re in the throes of such a decision, in the long run coming to that sort of realization can be a blessing for all concerned. However, I don’t think it’s a decision you should make hastily or when you are upset. And you should make it in consultation with someone whose greater knowledge you respect.
For the moment let’s keep the discussion specific to Second Level which implies that your horse’s stumbling block is probably the flying changes. There may well be a backstory to his situation. Is there a baggage in his history? Conformation issues? Unkind handling by a prior owner? Or is it possible that since you have never taught a horse flying changes, your own lack of experience and timing is the problem?
If you have someone get on to school him, don’t expect the problem to be solved in five minutes or two days. Two months might be more realistic! If their verdict is “Unlikely but not impossible,” your choices are three: change your goals. Plug along as you are, hoping that over an extended period of time things may change. (These first two solutions assume that you really like/love your horse.) Or get a different one!
This is not something to feel guilty about. If you’ve given it your best shot, and you’re not getting any farther after many attempts, it’s OK to come to grips with it. Remember, there are other things to play with—freestyle comes to mind or if you find suitable partners, pas des deux or quadrille.
You will not be the only one to have your dreams interrupted by reality. It happens to other stages too: at tempis or at piaffe and passage. Others get all the way to Grand Prix but recognize that what they can do is not CDI quality. You see it with event riders all the time. Then it’s not usually their dressage but more likely the horse’s courage or athleticism to face the bigger fences.
It’s also true that while the horse in question may have topped out before you reach your goals, he may still be a perfect learning tool for someone else coming along as you find a new partner.