Let It Go!
My advice is just write: write, write, write...but just as important: know when to let go. You must let go in order to move forward. Again and again I see young writers I admire getting stuck on one book. They try to get it published and nobody wants it and they go back and tweak it again and again for years without getting into something new. My advice is, "LET IT GO!" Stick it in a drawer, move on. Trust me, you will get better just by virtue of experience, and if you turn out to be Ernest Hemingway twenty years down the line, they'll ask you what you have stored away in that drawer of yours.