This reason’s a variation of Reason #2 (endlessly rewriting), but it’s a little more subtle.
By never quite finishing, you’re never in the invidious position of having a finished manuscript that you, or anyone else, can sit down and read and coolly assess. In some ways, finishing a manuscript is like a death in the family — or a lot of little deaths. You and your characters have spent a great deal of time together, you know each other intimately, you’re old friends — and now you have to say goodbye. What’s more, once they’re sent out into the world, your friends might be misjudged, disliked, even criticised. Better to keep them close where you can keep reliving and refining those lovely moments you’ve shared …
Here’s the solution
Get over yourself!
Finish up, type THE END, print it out, shove it in a drawer and start on something fresh. In a month or two’s time — when you’re well on the way to making new friends — take it out, settle in a quiet corner and read it through. At this point, you’ll almost certainly find a thousand little niggles that need unniggling, missing bits that need adding, fat that needs trimming and even whole segments that need re-ordering. Congratulations! This is the second part of being a writer: critically assessing your own work.
You might even decide it’ll take too much effort to fix. Fine. Put it down as a practice novel. Learn what you can from it and move on. Do you think Michelangelo carved David from a block of stone without spending years chipping away at countless other blocks, refining his technique? The mistakes ended up being turned into gravel paths while David ended up in the Galleria dell’Accademia in Florence.
The only way anybody ever learns to write well is by trying to write well.
This usually begins by reading good writing by other people,
and writing very badly by yourself, for a long time.
Now, get on with your writing!