I also have a lazy horse. But when I found out he could go fast - he suddenly likes to go fast now.
But from ground he is still a bit lazy.
When you circle him, start with a walk around the circle four or less times. Disengage him and walk the opposite direction. Once you have walked him both ways, ask him to trot both ways. Start by just swinging the end of your lead in the air. If he still doesn't pick up speed, continue swinging the rope closer and closer to the horse until it taps him. If he still doesn't pick up speed, increase the pressure and speed. Just continue this until he picks up speed. As soon as he picks up speed, stop completely and keep im going in at least half a circle to begin with. Do half a circle, then a full circle, then two, etc.
🔫 Don't Tread On Me 🐍