Fatigue is the first and most common symptom of stress, and it is also the most curable.
Fatigue is a direct outcome of stress. The mind shifts into a higher gear and consumes more energy, and the body assumes there is a physical threat and goes into a tense state of readiness. When this state is prolonged, the body starts burning the reserves and damaging the 'infrastructure'.
Rest very efficiently cures fatigue. With the conscious mind out of the way, the body is able to restore itself quickly and fully. However, the conscious mind also has to learn to overcome its problems, because the body can go through only so many cycles of high damage and high healing before making a mistake somewhere.
For long term, deep, and healing rest confusion and conflict of the conscious mind have to be let go. Take a five minute rest, get a good night's sleep, take a vacation - or change your daily routine if necessary.