Here is my advice:
If your horse runs put your shoulders back and lean back slightly while performing half halts.
If possible insert them on a circle and gradually make the circle smaller until the horse comes to a halt and calm state of mind
To teach your horse not to run I would work on transitions for example walk-trot-walk and if you feel save enough walk-trot-canter-trot-walk follow this process until you horse learns to obey your aids. If he keeps running try to lounge him before riding and work the transitions.