One of my pet peeves is when someone brings in a horse for training and they lead them into the barn while having a death grip on the lead rope right below the snap. The horse is usually tense, walking all over the person and leaning on them, with the horse leading the person instead of the person leading the horse. The horse has learned to brace and pull against being braced and pulled upon. If someone grabs you by the sleeve of your shirt or better yet, the collar of your shirt and tries to drag you along; your first response is to brace and pull back. Same deal with your horse. By teaching your horse to lead on a slack lead, rather than a taught rope, your horse will learn not to brace while you are handling them on the ground.