To know you are different, you must first know who you are. Even the person who knows he is extraordinary through not knowing his identity has an idea of who he is. He knows he is nameless. He knows he is without a place in life. He knows what he is not. Only once he has acknowledged this can he realize he is unusual.
Once a man realizes his differences, there are several paths that he can follow. He can reject his individuality in favor of being assimilated and "normal." He can compromise, keeping some of his own traits and adopting some of society's. He can accept his differences, welcome them, and continue governing his own actions and thoughts.
Two of the paths are flawed.
To reinvent oneself totally is to abandon who you are, to create an entire new personality. To refuse to change completely is to deny that your differences may in fact be failings. It is only the man who is willing to compromise who truly knows himself. He is able to see both his strengths and weaknesses and is willing to embrace them both.
I have always known I was different. I suspect I still am.