I think talking to yourself is normal, not always "good" normal, but I think it's a common coping behavior. For most of the last two years I was totally alone, physically sick, and very depressed. I was really stressed and frustrated about trying to earn a living and having a place to live. The talking got pretty bad. Like you said I'd be walking and talking, when all of a sudden I realize someone is coming toward me, and I was embarassed. They probably don't think anything about it though, because I'm sure everyone has done it.

My problem was that I would always complain or argue. I was upset about something and would get myself all worked up. It just made everything worse. The only way I've been able to do anything about it (apart from not being alone all the time) is to simply stop myself cold when I notice I'm doing it. I just drop it. I focus instead on my senses, what some people call mindfulness. I listen to what is going on around me. I look at the flowers, the buildings, or the ground. It's hard to stop, because you are talking for a reason, you have something on your mind, or something to express. So I have to remind myself that the talking and thinking I'm doing aren't accomplishing anything, and I'm just on auto-pilot.

It's like my brain wants a habit. It's just going in circles, even if I'm actually thinking about something. I think the same things over and over again. The talking is just an audible version of what's going on in my head. My brain seems to want to be occupied with the thinking and talking, but it actually takes me away from reality, and I have to force it to stop. The thoughts and talking have "inertia", just like a a physical object. You mind is in motion and it wants to continue doing same thing over and over. I don't think that stopping altogether is something you can easily do. You have to be patient, and keep trying over and over when you are in the habit.

I get the impression that a lot of people have sleepwalked at least once. I don't know for certain, but I'm pretty sure I did it once in high school. I think most people, if not everyone, has woken up yelling or something. By saying that "everyone does it" I don't mean to dismiss your concern, just to point out that those things don't make you "crazy", as you say. Maybe really stressed out.

I also think that we have a need to be heard and acknowledged. When that's not happening, I know I keep talking to myself about those thoughts or feelings. It's like I need it to come out, but talking to myself doesn't offer any relief, because I wan't someone else to hear me. A lot of times I don't really have to say it to anyone, I just need someone to acknowledge me personally in some way.