A soft flexible horse is the ideal that you are working for. At the same time, we are working on leading the horse and how to react to our posture. Ask the horse to move off of pressure from the lead rope. Release immediately when the horse gives and reward. Ask the horse to stop, you may have to get your body posture real big to emphasize the stop transition.
Rest is important too.
We like to give the horse time to think about what happened while we were working. When the horse has done what we ask, we will let him stand in a relaxed posture and think about what we just did while we are rewarding this behavior. The ability to longe correctly is incredibly essential. Longeing is not about exercising your horse. Longeing is used to teach a horse direction, posture, how to yield, how to move their feet, and move off pressure.