First start by shutting out your internal critic and editor. There is a time and a place for your sharp editorial skills and your critical eye. But writing early drafts is not the place or time. Make a deal with yourself to postpone checking for spelling, punctuation, syntax and overall excellence until you have made some solid decisions. Those include:
- Deciding what's going to stay in your story.
Where in the manuscript everything will finally be.
Eliminating all the flab that needs to be cut.
Once you have worked your way through enough drafts to have finalized the above, that's the time to start getting picky. Doing it any earlier is a source of productive avoidance. It looks like writing. It isn't. It's tinkering too early.