Exercise is a big one. I recently started up on wellbutrin/bupropion antidepressants which also were prescribed to give me more energy. and its been 3 weeks and its definitely better. some 5-htp pills may help. As well as taking B-complex pills and creatine. My friends and I have noticed a huge gain in energy and a high increase of dreams remembered after taking 2 B-12/b complex vitamins with creatine. (creatine has also shown to combat MDD major depressive disorder). But yeah, go to a doctor and see what they can do, I do suggest the B-12 and creatine.
I think work mostly drain us physically and mentally. So unless we can reduce long working hours to more reasonable hours, we would continue to feel drained no matter how much medication or supplements we take.
I get tired when I've slept too long. I function best on 4-6 hours of sleep. Anything more than that and I'm tired alllllll day.