Living changes people. As a matter of fact, life changes while living. People who are now old were young once, and there are numerous accounts of the rich and powerful losing all the money they may have accumulated through their work. I said that to say- while being alive, many things can change. Although this is true, the one thing that should never change is oneself. If times become turbulent and hard to deal with, how far from the norm would you go to maintain yourself? If you knew today that the world is going to end tomorrow, would you go out and indulge in every sort of lawlessness? If everyone is jumping from cliffs would you? In knowing yourself, you must be able to think for yourself, you must be able uphold your principles and beliefs, and you have to know what you are capable of.
I have seen very trustworthy people lose themselves by cheating or stealing because someone encouraged them to do so. They surrounded themselves with horrible people, therefore they eventually changed in an effort to 'fit in' or be like everyone else. To know yourself doesn't simply mean knowing your name, rather it also includes upholding the life lessons you have learned and endeavoring to maintain them in the face of those who challenge your character or integrity.