If we take the tennis example and apply it to the everyday process of sitting and standing, we can learn a lot about our posture and how we may unconsciously tense muscles that are not designed to be contracted. Imagine that your neck muscles are like your foot which is applying pressure on the brake of your car. It is useful to be able to stop your car in this way. However, we are designed to move with a lengthened spine and no brake action is ever required. Stopping can be accomplished without tightening the neck muscles and by having balanced tension throughout the whole body.
Try this: come to the edge of your chair, put your hand on the back of your neck and begin to think about standing up without moving. Can you detect tension in your neck? If that is the case let's bring some new thinking to this process. (Even if you don't notice any tension, continue on........). Now, without physically doing anything, think your neck to be easy, relaxed, or free and then move your torso weight over your feet and continue to notice the addition or absence of tension. Stand up and continue to notice your neck. The good news is that if you felt tension in your neck, you have recognized your habit of compressing your neck down onto your spine. Better news is that your new thinking may have very well resulted in a freer neck and a more upright posture as you stand! F. M. Alexander spent years dealing with his habit of taking his head back and down onto his spine and recognized in the process that postural habits are strong and ingrained. His greatest discovery was that habits are more successfully modified when our nervous systems are calm and open to pausing before action.