Self talk, as I understand it, is a way of reprogramming your mind. It's taking those old tapes that play and erasing them, and replacing them with tapes that serve you better. And it becomes the tapes your children play in their minds, so hopefully, they don't have to do the "unlearning" that we do. Especially if you self talk out loud.
(And I think we SHOULD self talk out loud, I want my child to hear me struggle, to hear me replace my old bad thoughts with better ones.) As the saying goes, change your thoughts, change your actions, change your character.