Auto correct

I've noticed that when I'm chatting with someone online and I make a typo, I will automatically "correct" it--usually with the help of the *, even if the actual meaning is obvious. I'm not sure why this is. It seems like wasted effort. For example, I often mistype -ing endings as "inh". Anyone with half a brain knows what I mean, so why is it that I feel the need to "fix" it immediately.

Exmaple:

Friend: [[says something sad]]
Me: sounds depressinh

Me: *depressing

WHY do I do that!? Do I really think my (highly educated and intelligent) friend is going to think I meant "depressinh"** and stop the conversation to google that word and figure out what it means because he is unfamiliar with it? Am I afraid that he will interpret it as a depressed hyperbolic sine function*** and try to figure out what I am talking about mathematically and how it relates to his situation? Am I so concerned that someone will think I don't know how to spell the word "depressing" that I have to fix it so they know that I really know how to write it? I don't know. But I continue to do it.

**ironically, when I wrote this word, I misspelled it "depressing". ha.

***ever since I wrote that I can't stop seeing the "sinh" at the end... the the point where I have to really concentrate to figure out what the word is supposed to be. Great.