When you over-think things and constantly relive your past and preplan your future, you essentially step out of the present.
Constantly over-analyzing your circumstances, interactions, and choices can lead to sharp or throbbing headaches. Shake off your fears and doubts, shift your concentration onto something else, and bring yourself back into the ‘now’.
Obviously, stress, tiredness, and overwhelming schedules can also lead to headaches. But generally, you will find they occur when you are dwelling too much on the past or future. Being present and focusing on your ‘now’ will help relieve your headaches. You need to distract your mind from your current thought processes.