Very, very rarely do I talk to myself intentionally - usually it's when I'm alone all day and I feel that I need to be in some kind of conversation so my mind doesn't start getting... numb, for the lack of a better word. I find when I'm on my own for long periods without conversation - especially indoors - that I get headaches easier and sounds tend to annoy me more than anything if they constantly come from the same direction. Talking out loud makes sounds bounce off walls differently than a TV or a PC or whatever, so yeah. Singing works, too.