The great majority of us are required to live a life of constant, systematic duplicity. Your health is bound to be affected if, day after day, you say the opposite of what you feel, if you grovel before what you dislike and rejoice at what bring you nothing but misfortune. Our nervous system isn't just a fiction, it's part of our physical body, and our soul exists in space and is inside us, like teeth in our mouth. It can't be forever violated with impunity.
If you don't like your own character there may be a new one ready-made and waiting for you. The snake sheds its skin with impunity, relying on the same nature which you rely on.