These words are a translation of the concluding words of the Lun-yu, or Conversations of Confucius. They are proceeded by admonitions to know the "decree" and the rites.
Several quotations could be chosen as being conveying the "central message" of Confucius, and I don't know if this is the one that scholars of Confucianism have chosen. If they have not, it is because they don't realize how much these words would be foreign to Semitic or Indo-European ways of thoughts, which from ancient times to today have always gone elsewheres in there quest to understand people, when they deemed it worth their notice to pay attention to anything as petty as people at all. On the other hand, this statement by Confucius reflects either the presence of humanism in Chinese philosophy at this early date, or was a sign of how Confucius shaped Chinese society into the mold of humanism.
In most world traditions, human society has been seen as either an instrument for some external goal, or as a ephiphenomnea of either natural or supernatural forces. To try to sort out human life by what was already at hand, the written language and the spoken language, and how it was used in social activities, seemed to have never occured to be a notable influence in the religious or natural thought of the thinkers of India, Israel or Greece. Human society was conceived of as the creation of a divinity (as in the Tanach) , or a tool that will eventually reach a perfect society (The Republic). For some reason, these petty words were never considered to be a factor in understanding human life. Perhaps it was a matter of people fearing infinite regress, if the self-defining verbal world was used as a guidepost, verbal meaning wouldn't mean anything, it would just be a game. So they had to be grounded in something, such as concepts of divinity, especially with the Roman Catholic Church, and its entire social organization of Europe. Human nature could be understood as a result of the Divine Will, and human words were meant to either reflect that, or to be tools to further implement the divine will.
I will have to skip describing the history of this idea through the middle ages, renaissance and industrial age in Europe and America. Instead, I will skip to the present day, when the notion of divinity is not the all defining principle of society. However, this doesn't seem to have freed people from their superstition and fear. People stil try to sort out their emotions and dreams by explaining them in terms of blind, arbitrary, impersonal forces. Except for now it isn't a succubi tempting you into illicit sex, it is a habituated dopamine plesure center. And it isn't the devil tempting you into the sin of wrath, it is a genetic predisposition to aggressive behavior. Gender roles were not created by God, or the result of Eve's disobedience, but are the results of a series of hormone mediated behaviors. Call these what you want, but all that has taken place is that one series of blind impersonal forces has replaced another as an explanation of human life, when the most normal explanation of human life would be to examine what is in the contents of our emotions, and how we use words in our day to day discourse.
Strangely, this belief in blind impersonal forces has not only gained a descriptive certainty as an explanation of human life, but a prescriptive meaning as well. One of the things that I find most ridiculous about the debate on homosexuality is the debate on whether or not is is the DNA, a debate that seems crucial to both pro- and anti- homosexual sides. Why does it matter whether or not someone's DNA "tells" them to have sex with people of the same sex? Does the presence or absence of this DNA mkae homosexuality any more right or wrong? Why does a "homosexual gene" telling you to be homosexual have any more prescriptive truth then your neighbor's dog telling you to go out and kill people?
This, then, is the situation in the 'West', a constant searching for some kind of outside force to explain human behavior. Although Chinese society has never been perfect, and could be very cruel, repressive and superstitious; the Chinese culture has never sought out an outside force to explain their society. They have always started with the world of words, and of natural human emotions, to explain their society. And the consequences of this teaching, that people can be understood through their normal words and discourse, was to be a guiding principle of Chinese society.