That is motto or joke we often hear. Now I am reading the writing about that in a blog. The author shares her experience during studying at Princeton and relates it to the motto. He writes in the article that to work hard and to play hard is a way of life, both must be in balance. His experiences during the study are written there, whether it was the time to work hard or time to play hard. He studied and concentrated well in some nights, then went out for some drinks with friends at other night. That is a great life, if we work hard only, we might be too serious to enjoy this life. If we play hard only, we might pass and lose every opportunity that comes to us. Read in this article about how you should be doing.