Fatigue is an early sign of mild dehydration, according to experts. Staying on top of your liquid intake will keep you fresh. Though you can get a third to a half of your daily water needs from food, you still require eight-plus cups of fluid to feel right. Make sure at least five of them are water, say experts, and add a cup every time you down diuretics -- beverages that drain body fluids -- like coffee or liquor.

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