Have you ever stopped to consider that maybe your lazy horse really isn’t lazy but he is biomechanically undeveloped.
This means that he is not strong enough structurally in order to complete the task that you need him to do.
Or have you considered that maybe you’re lazy horse isn’t really lazy because your cues are not coming across as readable and so therefore he is kind of like I don’t understand what you’re doing or what’s going on up there so his lack of response is actually to protect you.
Or that the lack of forward movement might be pain? If it is pain causing the “laziness”, you’re not just going to “ride him out of it”.
When our horse struggles to move forward, we must ask why and continue to investigate, and not continue to just push him forward as we may end up doing more damage than good.