It is you, but you’ve convinced yourself that you are separate from it. You deny it’s existence, which is fine, but the exact moment it attacks (assuming that you haven’t succeeded at destroying your soul by that time) you will truly be broken. The part of you that you hated will separate itself from you; you’ll then come to understand the true meaning of hollow.
Broken, half the person you once were, a shadow of your former self (because you no longer have your shadow self to protect you), you will be vulnerable to attack . . . Perhaps even possession?
(Do you really want to know?)