I used to say that when I want an intelligent conversation, I just talk to myself. Yes, that may seem egotistical, but I just think of it as having a healthy self-image. I feel that most people probably think they are smart, or think they are smarter than they are. Do people really walk around saying, "Hi! I'm an idiot!". They may say to themselves, "Well, that was dumb." But deep down inside, they don't really believe they are stupid.
What better way to judge yourself than to talk to yourself. Of course, you could ask your friends their opinion, but they are your friends after all. They will either like you enough to lie to you, or are your friends because you're smarter than them, or are your friends because they are smarter than you and can easily manipulate you and will therefore falsely build up your confidence in order to get you to do their bidding later. Or maybe they will be brutally honest with you because they are your friend, or because they are the type of person who likes to put other people down, in which case begs the questions, "Why are you friends with that person?" Let's face it, they are in the same boat and secretly think they are the smartest person.
They used to say that the definition of crazy was not talking to one's self, but answering one's self. That was probably started by a crazy person. I am sure they were probably talking to themselves when they came up with that.
I say the real deciding factor is what you address yourself by when talking to yourself. Do you call yourself by name...all third person style which is silly,...or do you say "self"....as if someone else was listening,...or maybe you're one of those oddballs who use "I" or "me". I say you shouldn't use any address, because you know who you are talking to.
So, is it healthy to talk to yourself? I say YES........unless you're an imbecile.