Make no mistake, Nicklaus' original tenet, as taught to him by Jack Grout, who used to hold his hair while he swung, was often criticized by such teachers as Jimmy Ballard for being too restrictive and even causing a reverse pivot.
But swinging around a steady head can really help a golfer who has trouble making solid contact or is lacking consistency. Here's what Jack (through Ken Bowden) wrote in Golf Digest some 30 years ago, and it might help you today:
"To me, a very steady, if not rigidly immobile, head is the supreme golfing fundamental, mandatory on every shot from a drive to a tap-in. I even have gone so far as to call this the game's 'one unarguable, universal fundamental.' Here's why I believe it is so critical:
"--The head is the hub of the swing, the axis of the club's rotation around the body. Move the axis and you move the arc along with it. This may not make consistent clubhead delivery impossible, but it sure adds to the challenge.
"-- To me, power in the golf swing comes principally from leverage, which is largely the product of torque--to oversimplify a little, winding yourself up like a coil spring. Try winding a coil spring that has play at its anchored end--the head in the golf swing--and see how much torque is lost. In other words, the more you sway or bob your head, the less leverage you can develop.
"-- Head movement changes the line of vision, and sometimes the sense both of target and swing path that promotes proper downswing form. Also, moving the
"--The disproportionate weight of the head to other body parts exerts a strong influence on stability. Thus the more the head moves, the tougher it becomes to stay well balanced throughout the swing."
Jack says that to engrain the feeling of a steady head throughout the swing, short of having someone hold your hair as Grout did, is to have a friend hold the grip end of a club lightly on top of your head as you swing.
This is also something that Paula Creamer's caddie often does on her practice swings. It tells you instantly if your head is moving up or down or sideways. If you do this in practice, chances are your ball striking will improve pretty quickly when you play. Give it a try.