Don't stop. Don't look back. Keep plowing forward.
That nagging voice in your head telling you that a character needs renaming, a sentence needs fixing, or a scene needs rewriting? Drown it out by concentrating on what comes next. This not a casual walk where you pause to take in the scenery, this is a full-out sprint!
I am frustrated the story that sounds so wonderful in my head is coming out onto the page as a sloppy, disorganized mess. But as I am writing and trying to ignore that voice, I keep telling myself that first drafts are supposed to be bad. This is a time of getting to know my characters, skipping sections and leaving them to be written later, and writing out plot lines as they jump into my head. I can go back and fix everything later.