Numerous health issues like headaches and fatigue can be traced back to not drinking enough water throughout the day. Why does water matter? Your body is about 60 percent water. And proper hydration helps you produce saliva, keep your joints lubricated and flush out waste. Water also helps your body circulate nutrients and aids the digestion of foods. Drinking the proper amount of water every day is essential to good health. Losing as little as 1 percent of your body's weight in water can cause fatigue and affect your body's ability to regulate your temperature and heart rate .