We often tire ourselves out through continuous flow of useless thoughts.
Sit comfortably in a quiet place with your eyes closed. Notice the thoughts that are flowing past in your mind. Do not try to block or alter anything. Just sit quietly and observe your thoughts like a third person. Avoid getting judgemental about what you are thinking. Just let the thoughts flow. Do it for as long as you feel comfortable - 2, 5 or even 10 minutes.
While a few of you will notice a peaceful calm mind, the majority would notice completely useless thoughts, memories, concerns, opinions randomly floating through the mind.
Are you surprised at why you feel so exhausted all the time?