The same thing with the body. You think that you need a lot of sleep, but might find that you can deplete your body by too much sleep, and develop the ability of going into deep sleep fast. I said the other day that there's a curve of sleep, like the first few minutes or hours it takes until one goes right down into deep sleep, and then the curve comes back again. The most precious time is that period, which might be just one hour or two hours of deep sleep in the night. So if you can get into just that deep sleep right away and stay in deep sleep a little longer, then you are able to sleep less long, whereas there are people who sleep superficially and don't get the proper rest. It isn't necessarily so that physical sleep is a help to you, but you have to know how to sleep.