Well, you probably do need a nap. I mean are you the type who ignores your body and just never takes the nap? You might require a nap-a-day in order to make it through. Ok, lets say that’s not the case. Well your body gets tired due to lack of use and lack of oxygen. So either you aren’t exercising or you aren’t breathing. So try to add more of both, and take a nap now and then and the feeling will eventually fade. Or else you can be like somebody I know and just decide that you have Chronic Fatigue and then use at as an excuse for everything.