I don\'t know what you mean, but I will say that I\'m a hell of a lot less formal RPing than I ever will be when I\'m writing fiction with the potential of publishing (not that I ever finish anything, but one can dare to hope).
RP is an escape from reality, a place to have fun. If you want to improve your writing, read a greater range of books by different authors and look at how they write stuff. I don\'t know, other than to pay attention to what you\'re writing and read it aloud to yourself to see if it makes sense or sounds good. It should make sense and sound good when spoken out loud.