A horse cannot master, learn & develop complex movement patterns from only attempting & repeating the movement pattern.
When we understand how a horse learns, we understand the facets of the response - and therefore how we need to shape, mould & build this response to reduce stress, which when rushed, conflicted or progressed incorrectly can lead to poor learning outcomes & both cognitively and physically damaging movement patterns. Horses are context specific animals. They experience their world very much in the exact moment. Humans speak of photographic memories, but horses experience experiential memories - as a snap shot of time. They learn, from experiences in their world, in 2-3 second cycles. Of benefit, neutral, or threat.
To develop complex movement's, we must break down each aspect of the movement into the 'now' for those horse. The truth of the horses experiential 'now' in learning, is from one stimulus, to a connecting response, and reinforcing moment at a time. Coinciding stimulus is either conflicting, or overshadows the response to develop a different learning experience. When we expect the horse to carry the foundation, the structure, and the facets of the movement we ask of it at the same time as refining the shape of it... we ask too much. Every complex movement pattern is a series of individual movements. Break it down yourself, then progressively bring it together with the horse's understanding and competence at every additional 'brick'.