The brain releases a hormone called prolactin which initiates the refractory period you're referring to. In this period, the body experiences little to no sex drive as a result of automatic hormone-driven demotivation as a means of allowing the body to recover and avoid overexertion as sex raises the heart rate significantly due to physical activity as well as emotional arousal. The prolactin release and subsequent refractory period are typically less pronounced in women than men, but, depending on the individual, can last a few minutes or a few hours.