My doctor, who is ridiculously awesome, gave me this sage advice on keeping yourself healthy.
- Eat a wide variety of foods. Make sure the foods you eat are colorful.
- Drink at least 2 liters of water per day. You should be peeing clear by noon.
- Eliminate as much stress from your life as possible. Whether it's religion, nature walks, or any other kind of spiritual work, give your immune system a rest by being at peace with yourself.
Also, a note on not being tired (especially for us college students): no matter what time you go to bed, always get up at the same time every morning. This sets your internal clock. The specific time doesn't matter, only the consistency. If you're out until 4 AM Saturday night, Sunday will be a bit rough after getting up at 6:30, but the next three days after that will be much better.