I relate to this alot, I will talk to myself an answer myself and the two sides of the conversation will have very different ideas.
While I'm going about my day I have someone talking in my head, not a physical voice but something I can't control, and it changes depending on my mood.
Some times its 'why are you bothering you'll fail?'
Other times it's 'wow we're amazing,'
I believe there is 2 people inside of me, I think of myself in terms of we, us etc, I think I'm a living version of Jekyll and Hyde.