Many people only drink when they're thirsty. But the truth is, we need to drink water regularly, even if we're not feeling thirsty at all. Remember that our bodies are 70% water, and we need to maintain that balance all throughout the day. A good rule of thumb is to drink 8 glasses of water a day, but in actuality this doesn't take into consideration the height and weight of certain individuals. A more acceptable rule is to take your bodyweight in pounds, and halve that, and drink the amount equivalent in ounces. For example, if you weigh 200 pounds, you should drink 100 ounces of water daily.
Water is truly a miraculous substance, giving us life. That's why we should always keep ourselves properly hydrated throughout the day, and drink even if we're not thirsty.