Sharing Responsibility
There is always a reason when things go wrong and we have to accept at least half of the responsibility. Remember it is we who are asking for certain acceptable behaviour if we have not defined what is actually acceptable then the horse is right to be wrong.
Once horses are further along in their training problems can take on a different dynamic. When a horse is inexperienced with little or no understanding of what our expectations are the problems are usually pretty obvious and relatively easy to diagnose if we start working backwards from where things went wrong. If the horse that is generally reliable and predictable starts to misbehave in certain predicaments it is easy to jump the gun and assume that the inappropriate action is situational. This can be the case but there might be more below the surface than you think.
His riders normal correction was to try and regain his attention when he would get distracted and this caused him to spook and overreact.