Horses have bad days too. Several horses/riders who were favored to win the jumping events did really crappy (knocked over the rails)and didn't even place.
Horses tampered with by Obama agents......facepalm.jpg.
I remember (years ago) when I had a sheltie and we were training for obedience work. I went to a "meet" to watch some other dogs work out and there was a German Shephard working out in one of the rings. This was a experienced obedience dog at the top of the ladder for awards (a UD, I think). Well, this dog just decided that, that day he wasn't going to do it. He was just lolly-gagging around the ring. He wouldn't go over the jump. When the woman got out of the ring with her dog, she had friends waiting and they were all laughing about this as this was very unusual behavior for this particular dog.
So, yeah, animals also will have days when they just don't want to work.