I remember that, when I was young, I was kind of amazed at how old men would talk to themselves, but now I do it. I am not yet so far gone that I talk out loud with others around, but I find myself vocalizing my thoughts to myself when I am alone (or think I am alone).
I wonder why we do that. Why, when our minds are clear, do we nonetheless talk out loud to ourselves, just repeating orally what we have already thought.
In Lord of the Rings, Gandalf explains that he talks to himself because it is a good decision to speak to the wisest person who is present. That sounds nice. I talk to myself because I am smarter than everyone else. Yeah, I kind of like that.
But, maybe, it is something else. Maybe it is just that I want to share my thoughts and do not feel I have anyone to share them with. This was the Red Green theory. His view was that people are right when they say that we need to express ourselves, but husbands know that there are some things which ought not be heard, even if they need to be said. That is why men have garages.
But I think that, perhaps, it really is a function (for me) of my frequent teaching and preaching. I grow accustomed to speaking my thoughts out loud. When I preach, I do not write everything out, so that what I say is heavily dependent on what I just said. By speaking out loud, I hear my thoughts and respond to them.
Ultimately, though, I think it is difficult to know why a man speaks to himself. The Bible does not say, but it gives an interesting warning: "A fool gives full vent to his spirit,but a wise man quietly holds it back." Pro. 29:11. If we speak to ourselves because we lack control, it is not a sign of wisdom, but of foolishness. Quiet is always more suitable than noise, unless one is speaking wisdom.
Having heard myself often over the years, I think this is something to keep in mind.