Energy Boost
Ayurveda offers an explanation—and some cures—for fatigue.
Unusual mental or physical exertion, stress, and lack of sleep can make people tired. Prevention in these cases simply requires self-observation. Sometimes it means not pushing the body and mind beyond their limits. Other times it means walking or doing some physical work to help increase the body's energy level.
Other major causes of fatigue include anemia, low gastric fire, and weakness of the liver.
If the fatigue is due to anemia, eating iron-rich foods and blood builders such as pomegranate juice, grapes or grape juice, and beets or beet/carrot juice can help. 
Right-nostril breathing (Surya Pranayama) is also helpful; it stimulates the liver, which plays an important role in building the blood.
For fatigue caused by physical exertion, drinking fresh orange juice with a pinch of rock salt gives a quick boost. Add 10 drops of lime juice to help the body cool down.