I talk to myself all the time. All. The. Time. It's a habit that began in childhood, which I think is pretty common. I'm sure there are far fewer kiddos who don't talk to themselves than those who do. Actually, I'm sure most of us probably still talk to ourselves on a daily basis. I know, for me, it comes in quite handy whenever maths are involved. Or editing (my jobby-job)--reading out loud is an essential aspect of my work.
But I also find that I spend more time than I ever imagined talking myself out of/down from x or y, peppered here and there with a much-needed pep talk or the so-very-tired, go-to mantra, 'you can do anything for an hour.' (Thanks for that one, btw, Amy G--it's been of enormous use).
Beyond those rather obvious applications of conferencing with oneself is this: I think cultivating a deep friendship, a trusted relationship with oneself is vital to wellbeing. Keeping information about ourselves to ourselves serves as a vital buffer between us and the rest of the world. We have, let's face it, so little privacy and so few private spaces left to us. Surely we must cultivate that kind of safe space within our own minds, if only to have a place in which to retreat when, for a startling percentage of our days, we are so very exposed.