The underlying assumption to the post is that somewhere deep within the turd being polished there is a nugget of gold.
It's not that so much as that in the process of polishing the turd, it's possible for you to realize you're working on a turd and start over again. That's part of the revision process.
One case that stands out to me was that in the writing of my novel, I had a 70-page part that I thought was great and slaved away on, then realized in one blinding moment that it was awful. I threw it away, rewrote the entire section over a day, and now it's the best part of the book. (I'll say in advance that the book wasn't exactly a nugget of gold, but at least I was aware of that when I published it. If I'd spent more time in it it could have become much better.)
It's not that so much as that in the process of polishing the turd, it's possible for you to realize you're working on a turd and start over again. That's part of the revision process.
One case that stands out to me was that in the writing of my novel, I had a 70-page part that I thought was great and slaved away on, then realized in one blinding moment that it was awful. I threw it away, rewrote the entire section over a day, and now it's the best part of the book. (I'll say in advance that the book wasn't exactly a nugget of gold, but at least I was aware of that when I published it. If I'd spent more time in it it could have become much better.)