Being a grammar nazi is not easy. It's not something you can control. It is not satisfying. It is annoying. Do you really think it's fun looking at virtually any piece of literature and seeing nothing but mistakes?
Do you know of the extreme dissatisfaction felt when you write something and realize that it is all wrong?
It's even worse when you're fighting with someone and spit out something that makes no sense in any known language.
Or when you're screaming at your cat because he took a crap in your room.
I don't get any satisfaction out of pointing out the difference between your and you're; the difference between their, they're, and there; or why you put "greater than I" instead of "greater than me."
It's just an OCD thing.
Update: I left the incomplete sentence as a kind of "self-taunt"... and everytime I look at my blog I feel a little sick and neurotic inside.