Train to become progressively more relaxed.
When I first started my study of Aikido the sentiment above was stated simply as "Relax Completely." Shortly after leaving Ki Society and forming Kokikai, Maruyama sensei changed it to "Progressive Relaxation." He reasoned that complete relaxation would leave one with the structure of a cooked noodle, no form, no strength. He wanted to preserve the idea that relaxation is an integral part of coordinating mind and body while doing away with the notion that complete relaxation was attainable or even desirable. Keeping with the idea proposed in my previous post that these "principles" are really instructional guidelines I rephrased "train to become progressively more relaxed."
A coordinated mind/body is greatly facilitated by a relaxed mind and relaxed body. A stiff mind is a mind that cannot be emptied, that cannot cede conscious control over the body. A stiff mind remains separate from the body thereby preventing the occurrence of mind/body coordination. A stiff body is a body that is partitioned and cannot move as an integrated whole. Whenever I lock a joint I disrupt communication across that joint and weaken my structure. If I use muscle tension to ward off an incoming force I provide uke with a place to "rest" since my tensed muscles prohibit the body part being loaded from passing the force along and being dissipated. When my mind and body are relaxed incoming forces have no where to land and be applied.
My relaxed mind is sharp, my relaxed body is strong, integrated and free of tension. My coordinated mind/body is my most dependable state. As I continue to train I become progressively more relaxed, more completely integrated, more "One Pointed."