Drink before you feel thirsty and until you’re passing clear or pale yellow urine [WebMD]. Aim for about 2 liters of fluid per day (more if you’re sweating or sick) [Anding]. Carry water and keep it by your desk and bedside. When exercising strenously, drink something with electrolytes [Anding].
Dehydration weakens muscles, harms concentration and coordination, increases stress, and fouls the breath [Loehr, Amen]. “Dehydrate a muscle by as little as 3 percent, for example, and it will lose 10 percent of its strength and 8 percent of its speed” [Loehr]. Chronic dehydration harms the heart and brain, contributes to obesity, ages the skin, and shortens life [Amen]. Due to a lag time between actual dehydration and the feeling of thirst, “thirst is an inadequate barometer of need”, and this barometer only worsens with age.
Daniel G. Amen. 2010. Change Your Brain, Change Your Body. Three Rivers
Roberta Anding. Nutrition Made Clear. The Teaching Company
Jim Loehr and Tony Schwartz. 2004. The Power of Full Engagement. Free Press
WebMD. Drinking Enough Water.