It all begins with a healthy foundation… nutrition, hydration, fitness, and sleep. Start by optimizing those basic needs and it will probably do the trick for you (especially since I have the impression that you are young).
If you still get sluggish even though you sleep plenty, eat well, get lots of nonalcoholic and caffeine-free beverages, and are physically active on a regular basis, consult a physician and exmine your family history. Perhaps there is a genetic predisposition to some condition that could be at fault… it could be as simple as a vitamin deficiency because your body doesn’t process things the same way as most, for example. But you (and we) can’t know that, so a physician may want to do some basic tests and then go from there.