Someone in an online group asked what she should do with the book she's written, and how she'd know if it was done. Having only limited experience in writing and publishing, I gave her my opinion. Still, the questions got me thinking. "How do I know when it's done?" or "How many revisions should I do?" are questions I hear a lot from other writers.
There is no answer for this that will work for everyone. My suggestion to the author was to put aside what she'd written, and take a few weeks or months off. I think you need to give your mind a rest and get some distance from the story. As a writer, you are too close to the subject to be objective. This is why editors can seem harsh when they cut up your beloved prose. Some editors are harsh, but ordinary readers are going to make assumptions about your writing if they find errors, and plot holes.
I don't mean to rant about the writing and editing process, because you can find better sources than me without looking all that hard. Writer's Digest is a good place to start. You can also try reading this article on revisions
Even literary geniuses don't get the words right the first time. T.S. Eliot had The Wasteland almost halved by Ezra Pound's edits. (Well, that's a bad example, because I think Pound may have gone too far.) Then there's a story about James Joyce; the story goes that a friend went to visit Joyce and found him depressed and slumped over a table. (I'm paraphrasing here, obviously.) "James, what's wrong?" "It's my writing. I can't make it work." "How much did you get done today?" "Ten words." "But... James, that's wonderful--for you." "Yes, but I don't know which order to put them in!"
You want more proof of writers getting it wrong the first time? Just look at the Bard:
"Temperamental git." Rightly so. Speaking as a writer (and sometime editor), writers as a whole are a whiny, molly-coddled bunch. Don't even make me list the examples. And, writers? Don't get in a snit. You know it's true. On the bright side, no one's perfect, and at least you get to write books.
Now it's Friday, and I don't want to drone endlessly, so here's a link for you fantasy writers who are interested in writing trilogies. Or rather, it's how to get agents to pay attention to you. I'm sure it works even if you don't write fantasy, but since fantasy is what I write, and since fantasy as a genre has more trilogies than any other genre (source: my own head), then fantasy is what I'm going with.
That about does it. And if there are any writers out there who had their feathers ruffled by my comments, please know that my tongue was planted firmly in cheek. Now stop whining and get back to writing your magnum opus. Shoo!