Actually, often times, I have two voices in my mind. Both of them are still me, but they often provide different perspectives to a situation or talk to each other.
Occasionally, one of them acts as my conscience for doing the right thing.
Sometimes they just root each other on. For example, one voice says, "That's cool!" and the other says, "You know it!"
Yeah, weird, isn't it?
On the subject of internal monologues: I'm sure lots of people have them. What separates some people from others is how much they think about things. Some people just blabber non-stop all day and never give themselves a chance to think. In one sense, I think it's related to introvertedness.
Often times, people overthink things and start to have all sorts of negative thoughts or feelings. In the end, they're probably wrong to have these thoughts. In the case of OCD, people have something that, if they think about it, it gives them extreme anxiety, and causes them to become obsessed.
Another bizarre thing is when someone thinks having negative or violent thoughts means there's something wrong with them, and also gets anxiety.
So, a good tip is to try your best to have positive thoughts, because negative/pessimistic thoughts can make you depressed.
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Like a crow, I am always observing humans from my distant perch.