^have to disagree Saddlebag. The mood of a horse really DOES matter. Nobody likes riding a grump who may comply but swishes tail and grinds teeth at every request. If my horse is having a 'bad mood day' while I will not be a pushover and lax on obedience, I also won't keep pushing her. I will change my activity/lesson plan, cut the session short, or just groom and spend time with her and not work her at all. It does wonders for a horse's mental state, and this coming from the owner of a horse who was previously notorious for kicking, biting, grumpy, obstinate, lazy, cinchy behavior. Now she is a pleasure to be around not only for me but others as well.
Perhaps you only meant not to get upset at a horse for being grumpy, in which case I agree. But I had to say that mood really does matter.
OP, you've been just slightly berated on this thread, and I'm honestly not sure why... Anyway, have you tried liberty training? This is something you could do in the indoor arena, is great for building bond, trust, and respect with the horse, mentally engaging, and the horse is able to be freely expressive and energetic. If your horse has a favorite buddy you are allowed to work with, you could turn them out in the indoor together and give a couple swings of the whip to get them moving, they love playing and racing together (provided the two already get along very well).
"You can do something wrong for thirty years and call yourself experienced, you can do something right for a week and experience more than someone who spent thirty years doing the wrong thing." ~WhattaTroublemaker