I’m not one to give advice on the subject, (considering I drink about 4 – 5 diet Dr. Peppers and at least 2 cups of coffee daily), but too much caffiene will disturb your sleep at night so that your body isn’t getting the rest it needs, thus making you feel tired throughout the day. A lot of people find this hard to believe, (again, because of my terribly bad health habits), but I actually studied to be a nutritionist for a while. I don’t even remember why I gave it up. Anyway, I’m not a napper – I find if I take naps I onlly get more tired and have a headache the rest of the day. If I start to feel sleepy I just go take about a 10 minute walk, (preferably outside, weather permitting), and eat a healthy snack, like raisins, or nuts, and maybe one or two chocolates. Then I’m ready to plug at it again. If you don’t have a place to walk just do a few stretches, and run in place.