Muscle tension headaches are commonly caused by poor posture with the head in a forward position and elevated shoulders. This caused undo tightness in the muscle at the base of the head and tops of the shoulders. When muscles are tight in the base of the head this may compress the greater occipital nerve, which refers pain to behind the eye. So if you experience pain in the eyes or in your forehead try releasing out the muscles on the base of your head as shown.