Well, possibly. But since when is a little insanity a bad thing?
When it comes to taking on different attitudes with different people is actually considerate. I wouldn't make the same kind of conversation with my great aunt Penny or my mentally challenged great uncle Richard, as I would with my brother (that is to say, I wouldn't hold a conversation full of dirty jokes and innuendo with the former two individuals). My aunts would want to hear about my love life and health, not argue about who's a better indie rock band. Its about relating to a person better... I go to different people for different advice/conversation, and it's the same thing. I can talk to my brother about music and social issues, my mom about money and things that require life experience, etc.
As for the whole prophesies thing, you could just be exceptionally good at inferring things. Putting together clues and such. Or maybe you're the next Nostradamus. I'm not sure, I'd have to know what kind of prophecies you have.