Make a to-do list to keep your focus, and tackle the most difficult jobs first, when you're freshest.
Don't hand in assignments until you can recheck for accuracy.
To stay alert, eat small but frequent meals, and snack every four hours on healthy treats, such as yogurt or whole-grain bars. (Big meals are hard to digest and can drag you down.)
Do simple, unobtrusive stretches like rolling back your shoulders.
Find 15 to 20 minutes to close your eyes. Short spans of "twilight" sleep can boost your energy for five hours or so.
If you need coffee, drink half cups all day. It jump-starts your focus, but more than three or four cups can leave you frazzled.
Don't complain about being too tired, because a negative mind-set can wear you down even further. (You'll spare your co-workers, too!)