There is something to be said for sticking things out until the horse makes a change. For the horse to know that he can live through something, or figure out we aren't out to kill him, we have to stick it out until he makes a change. But it's a very fine line. We have to be able to see the tiniest sign of change and reward that instantly, otherwise we missed our chance.
I recently had a moment like this with my warmblood. His cantering on line has always been a little bracy and sometimes he would get unconfident and want to run. It was fear based on his part. So one day I was working with him on cantering and I decided I could do one of two things. 1) when he got bracy, etc. to shut him down and interrupt the pattern, or 2) leave him out on the circle going "crazy" until he made a change. I decided to go with #2. He ran around for about 7 minutes, or maybe longer, I really don't know, and then I saw him lower his head, blink his eyes, lick and chew and he threw slack in the rope. I rewarded him instantly and brought him in. That horse released sooo much it was unbelievable. Yawing, sneezing, licking and chewing, blinking, shaking his head, the whole bit. For 3-4 minutes straight! He had to go to a place that wasn't very good and see that he would be okay. Unfortunately this is sometimes necessary, usually for more extreme horses. In the sessions since then his cantering on line has never been better! He's soft, calm, and he consistantly throws slack in the line. So sticking it out, in an appropriate manner, is sometimes needed.