From my experience, authors tend to fall into one of two camps: those who are perpetually chasing new stories and those who are perpetually editing existing stories.
I'm one of those who is constantly being lured by new ideas. They pop into my head at any time, shouting "Look at me! Look at me!" and trying to persuade me to just write down a few scenes. I get ideas for fanfiction (I want to write a prequel about what happened in the Wolverine: Origin movie between the two brothers running away from home and showing up in the Civil War and an Agents of SHIELD/Avengers crossover where the Avengers learn Coulson is still alive and the secret why the TAHITI protocol worked for him), historical (I think it would be cool to write a prehistorical romance set in the transition from hunter-gatherer to agriculture, or one set in ancient Babylon, or a Bonnie and Clyde-esque one from the Depression), and dozens of other genres.
On the other side of the coin, I have some author friends who are eternal editors. The blank page intimidates the heck out of them but give them one full of text and they can spend weeks polishing it until it gleams like a diamond.
The challenge with that approach is that no story ever truly feels finished. Even New York Times Bestselling authors admit that they look back on their most popular books and wish they could have done things differently with them.
Successful authors have to find their personal balance between the two. You can't turn off the flow of creativity but can't get swept away in it either. And it's critical to polish and edit but not get bogged down in it.
For me (and other authors inclined to chase shiny new stories), there are a number of strategies that can keep us on task:
- keep a notebook or computer folder with ideas and inspirations so that they don't get forgotten
- set yourself a daily or weekly word count on your main work in progress, then any extra writing time can be used to explore new ideas and projects
- incorporate the new ideas into your work in progress (if they're suitable)
- focus on shorter fiction pieces which allow you to explore many different stories in the same time period as a long novel
On the flip side, for editors and polishers who want to bring the shiny to their work:
- set a daily or weekly word count on your work in progress before you go back to edit previous days
- set an editing schedule, with one pass for each type of editing (eg: description, deep point of view, pacing, etc.)
- insist on completing a certain portion of the manuscript before beginning editing
- make notes of any changes or edits you want to do so that you can go back and do them all in one pass
I have my computer folder full of files of notes and ideas, although I have to be careful because I find it's too easy to lose an afternoon, clicking open one file after another. A friend of mine, who is an eternal editor, forces herself to complete each manuscript to the 3/4 point before she allows herself to go back and edit any of the previous work. Both very different processes, but each of them works for us.