If things start to go wrong during your training process, it is important to step back and analyse where the issue has arisen from. Sometimes it can come about because the question you are asking is too big, you are confusing in your aids, or the horse is not mentally or physically capable of giving you the answer you are looking for.
In this session, with Cassonova, he really struggles on the change from the left rein to the right rein. After a few attempts at this, I finally was able to realize he didn't have enough foundations and understanding and I needed to take the speed away and help him to understand the answer better at a walk. By allowing him to go back to an easier question, he was able to start to piece together what I was wanting from him in a more relaxed fashion.