We've all heard it before: all writing is autobiography. It's the notion that who you are comes through in your writing no matter what you're writing. I think it's true. So the next question in the logical progression of things would be: who are you?
And what are you telling the world about yourself?
Everything you write tells about you. The content tells. The lack of content tells. The subject matter. The writing style. The tone. The way you treat your characters. The way your characters treat each other.
In a writing class years ago a teacher said, "If there's something wrong with your characters, there's something wrong with your character."
That saying stayed with me all these years, and although I don't pretend to know all of what it means, I think it nevertheless is packed with profundity.
Recently I saw a documentary on pop music producer (Hall & Oates, Aretha Franklin, Chaka Khan) Arif Mardin, and in it Quincy Jones (quoting someone else) said: "Your music can never be more or less than you are as a human being."
So then again, the next question in the logical progression of things: where are you at in terms of being a human being?
It seems to me, based on such thinking, that developing into a fine writer has a lot to do with developing into a fine human being.
Want a quick look in the mirror? Take a look at your writing. It'll tell you in no uncertain terms. Want to get better as a writer? Yes, you need to learn and develop your craft, but you also need to develop as a human being. Your "music" can never be more than you are.