I won't take time to repeat all the obvious benefits of physical exercise but will only underscore the well-attested fact that a program of regular exercise increases one's efficiency in every facet of life, including the depth and restfulness of sleep. And the time taken can be minimal; just a few minutes of calisthenics and running in place in one's room or jogging around the yard or block is often sufficient. Exercising doesn't take time. It saves time. Still, few consistently do it.