Reference #10: On Writing Well
Zinsser provides the following advice for ending a piece of writing: "When you're ready to stop, stop."
You don't need to provide a summary or belabour the point, lest you make the reader feel they're not clever enough to get the point.
Wrapping up a piece should only take a few sentences. A perfect ending should take the reader by surprise, but feel just right once it's over.
Zinsser. On Writing Well, 2006. (64-65)