I've heard that so many times and honestly since I was in high school and to date, it's hard for me to still be in search of knowing myself because I believe that when we know each other, we really live.
 "Know yourself" when listening to this little internal voice, with my arrogance and ego giving everything I say to myself: how can I not know myself, haven't I lived with myself all my life? Am I not myself all the time?
– Well, no, the truth is exactly the opposite: you don't know yourself and very few times in your life have you been yourself. What you know about yourself is your personality, your unconscious conditioning and programming imposed from generation to generation by significant people in your life, culture, education, etc.
The word personality comes from the Greek “person”.
The persona was the mask used by Greek actors in plays. So, your personality is the mask with which you relate to others, but it is not you.
Have you noticed that when you are alone and you think that nobody is watching you, you behave differently?
If you don't feel stalked, you act like you really are. Look closely, even with some people you are a certain way and with others you are different.
That's right, your personality is something acquired, which has to do with your childhood, with the society in which you were born, with external things. None of them you chose and over none of them you had control.
The question is: Do we always wear a mask to relate to others?
Always. A mask of learned attitudes, of commonplaces, of rehearsed reactions. A way of being and acting that leaves no room to be yourself, to be genuine: to be spontaneous.
We hardly make contact with each other. We avoid showing ourselves as we are to others.
We avoid it because we're embarrassed, because you've been told you can be anything you want… except be yourself. And in those rare moments when you make contact with your being, when you cry emotionally, laugh without thinking or dance without control, what happens?
– They repress you, they think you're crazy, they criticize you.
– That's right, others are uncomfortable that you show the real me, because in society you live in the "as if", in the superficial, in the comfortable, without making contact with the other. Showing your emotions, your vulnerability, your joy, your innocence, is crazy.