Have you ever used the phrase, “It makes me tired just thinking about it”? Henry Ford reportedly said something along the lines of: “Thinking is hard work. That may be the reason so few engage in it.” There is some truth to the notion that thinking is a strenuous physical activity, witnessed by the fact the human brain weighs in at about 2 percent of our whole body weight but uses up about 20 percent of the body’s energy supply.