Well, that’s not rocket science, but I think a writer needs reminding every now and then.
A writer makes new sales through writing new stories. It is more effective to send stories out than to keep tinkering with them until they’re ‘perfect’. Once a story works, send it out and write something new. If an editor rejects the story, it is more likely to do with the premise or storyline or general feel of the story than with the writing. No amount of tinkering will fix the premise.
If a writer has material on ebook sites, the best way to increase sales is to put up a new work. Yes, reviews are important, and yes, they need to be promoted, but readers who enjoyed your work are looking for more of the same. Give it to them.
If you’re marketing to publishers or agents, it’s more likely they reject your work based on the premise, character or idea than the minute details of the plotting. Writing something else will do more for your chances than trying to sell an existing, multi-rejected-almost-accepted novel. Put that novel aside and write something new.
A writer writes. A writer doesn’t complain on the internet how hard it is to sell, or get reviews, or… Only through writing new stuff can a writer prove that he or she is really a writer.
I rest my case.