The theory about interiour monologues is that they don’t really belong to you. Your inner voice has developed from years of familiar and societal affectation, and you can’t stop it anymore than you can stop breathing air. Of course, the voice will be very similar to you (whatever “you” is/are), but you have no control over it. It is an independent wandering stream of thought that just happened to sit through every boring class and hot date that you’ve ever attended.