Fuel up, but keep it healthy and simple. Some ideas:
Oranges. Citrus fruits are high in vitamin C, which is good for your immune system.
Nuts. Enjoy a small handful of walnuts, almonds, or pistachios for some omega-3 fatty acids that even out your stress hormones.
Whole grains. A bowl of oatmeal or a piece of whole wheat toast could help your brain make more serotonin, which can improve your mood.