Lots of people will tell you that it’s best not to revise, rewrite, or otherwise edit until a story is complete. To some extent, I agree. If it keeps you from continuing, don’t do it. That’s a pretty basic rule of thumb.
But not rewriting can sometimes delay you just as much. A very common case is that an idea introduced early in the story and then built upon is unfeasible, not what you wanted after all, or otherwise flawed.
You end up rewriting entire chapters, maybe even scrapping half the book.
But if you’d re-read what you’d had, caught it early, and knuckled down to change it before continuing, then it would have been fixed before you even reached your official stage of revision.
There are also the times when one is stuck regarding what to write next. Sometimes, that’s a sign of a missed problem, or just time to read back and remember the finer details.
It’s not even necessarily a bad thing. Unless it’s NaNoWriMo, and even then, I’ve increased my wordcount in revising occasionally. For every moment it slows things down, it pays off in making the rest of the writing go more smoothly.
Yesterday, I realised I had been writing an entire story arc with bad information. I had to refine my research, and correct a good deal of the story’s information and action, across three chapters.
But it solved my problem with what to do next. Once my information was correct, the conflict was better defined and the resolution became simpler. I even worked out the next obstacle and the segue into the last major character’s introduction.
Some people can use revision as a form of procrastination. But if there is a problem that is keeping an un-outlined story from continuing in a satisfactory manner, I think it’s best to identify and correct that problem. Just going on with the intention of editing at the end may make it worse.
I specify un-outlined because these stories are particularly prone to evolve as one writes. Hiccups and mistakes in the story can be devastating. I’m not saying everyone should always outline–I don’t, and I find that generally makes my stories better–just that outlined stories are less likely to deviate in an undesirable way.