Your head is like a big, heavy, round bowling ball sitting on top of your shoulders. When it is properly balanced, directly over your erect spine, much less effort is needed by the muscles on your back and neck in order to support it. By only moving it a few inches forward, those muscles begin to be strained. If you continue to keep that forward posture, with that heavy load, 48 to 12 hours daily, is there any wonder why you feel so tired? There may be other problems also, not just fatigue. There may be joint, muscle, neck, and back problems to go along with the poor posture. As you continue to slump, your body will naturally compensate by flattening the normal curves of your lower back and neck. This, in turn, can lead to pain and degenerative arthritis within the spine.