A piece of writing advice I rarely hear, but one that seems appropriate to our digital age, is to never throw any of your work away. Everything you write, finished or unfinished, even the trunk novel that will never see the light of day, is potential material for a future work. Those twenty thousand words you abandoned ten years ago may eventually be the core of a novel proposal next year.
I mean it seriously. Forests of the Night, Hostile Takeover, “The Historian’s Apprentice“, Prophets. . . all of these stories of mine were the result, at least in part, of resurrecting some piece of fiction I had abandoned, in some cases a decade before. Forests and Hostile Takeover were reworkings of short stories I had written before I was published, I had abandoned the first third of “The Historian’s Apprentice” six years before I came back and finished it, and the first chapter of Prophets was written, and ditched, shortly after I finished Hostile Takeover, and long before I had even contracted for a sequel.
And since I am between contracts, I am now eying a project I had initially started for DAW before I abandoned it 20K words in. At the time, around 1998, I was right to switch gears, since I saw no way of really finishing it the way the story had been going. Today, I have a much better handle on my skills as a writer (and after another 12 years writing, one would hope so) and the plot problems that seemed so intractable then actually seem pretty simple now.
So, storage is cheap. Back up everything, and don’t throw anything away. You will use it some day.