For writing, the material is essentially free. It's totally reusable as well.
Remember one of the first rules of critiquing: "The manuscript is not the story. The manuscript is an attempt on the part of the writer to recreate the story in the reader's head."
If you've killed the manuscript by too much reworking, laying it aside and starting afresh is essentially going back to the story.
You will bring to the new manuscript all the things you have learned in the reworking, but you will (it is to be hoped) have left behind all of the things that killed the first manuscript.
What you produce has a better chance of being new and fresh than any additional reworking on the old manuscript can give you.
And because you've reworked the old manuscript so much, you can still say that you are working with something, even if it is only something in your head. The story itself has become clearer to you through your efforts to convey it in the manuscript, even if the manuscript can no longer do the job.
[This message has been edited by hoptoad (edited July 17, 2006).]
Some people are better jumping right in a writing / coding without a lot of forethought. It can work in some cases, but I'd be willing to bet that deep down, they have an idea of what the final product is going to be like.
In the end, you're going to look at your manuscript and it'll be buggy . . . it'll be patched together in spots . . . you might have taken the entirely wrong approach in some places.
For example . . . one of my biggest problems is choosing the correct perspective to show events from . . . which character is goint to be the POV character. That usually happens when I haven't nailed down the events. I don't know exactly what happens. So I write the scene anyway . . . and it works, but not quite.
I come back at it to re-write it from scratch and now I KNOW what the events are, and I'm not worried about the details, 'cause I know them . . . and suddenly it's very clear what perspective I should be telling the story from.
That's the most obvious, and common reason for re-writing that I have. (as opposed to revising)
It would help if I could ever FINISH a story . . . gain a little more credibility.