In order for you to stop keeping your head down the chest should stay forward and not the head that stays down in your posture. In the backswing, if you start in a parallel position and you address the ball with a square club face you will need to let your head turn behind the ball. In the downswing the head stays in its position until the right shoulder comes through and will bring the head up into the finish.

What is going to happen if you keep your head down you will lose balance and rake yourself into your toes. When you finish your golf swing and you always finish on your toes your keeping your head down way too long.

It will improve your swing because now you will feel that you are accelerating through the golf ball and there is nothing in the way.