Most unfinished writing dies somewhere in the middle of the first draft. The cause is almost never lack of talent. It is the moment when the writer realises the draft is bad — and decides to fix it before continuing.
Why this kills drafts
Editing a half-draft is different work from writing one. It uses different mental muscles, and switching between them on the same project is the fastest way to stall. Allow the first draft to be bad. The fixing comes later.
A useful rule: do not reread anything you wrote until the draft is complete. If you must look back to remember a name, look only for that name and close the file.