A bit of synthesis here on useful comments. My feeling is--if you have ruled out anything medically worrisome that could be causing fatigue you may as well accept nature's beautiful gift of an afternoon rest or nap. This is usual in numerous (often hot) countries and can be a huge benefit in terms of recharge. I think the feeling of needing to be alert and productive all the time is in itself exhausting! Many creative thinkers like a nap--it is a mental reset. I've taken a nap pretty much every day starting in high school--and yes, I've worked full time (with a futon in my office!), been a single mom, and had many adventures so I don't feel I've missed out on being awake.