I was going to write more on Imposter Syndrome and self-image, but was intrigued by a related subject: self-assessment. Here's a possibly profound psychological finding: People who are high in a given trait or capability tend to rate themselves lower than those who are low in that same trait or capability. What does that mean? I'll restate:
Good people rate themselves as bad, and bad people rate themselves as good. For example, people who are very skilled interpersonally tend to rate themselves more harshly on interpersonal skills than those who are socially inept. What does this mean, and why should a writer care? See past the LJ Cut...
There are a couple of reasons why this is true. Why are people good at a given capability, including interpersonal skills? In part because they are fully aware of what it takes to do it, and try to fix their mistakes. You have to know what your mistakes are to fix them. This is an extension of the old principle that people learn best through their mistakes--but only if they can see the mistakes in the first place! If you are clueless as to your true capability, you can make any random mistake and not notice. In other words, you rate yourself high out of a misplaced sense of self-confidence rather than evidence.
"Aha!" some of you out there are thinking, "I think I'm crappy, this means I must be excellent!" Or, alternatively, "wait--I thought this was pretty good. Back to the drawing board..." Don't overthink this!
Perfectionism is someone who is endlessly trying to improve even when it is already very good. In writers or artists this sometimes manifests as the little critic in your head, or what one panel I saw called "the Watcher." Sometimes you need to make a distinction I had to learn as a newly-fledged management consultant: between good and good enough. If you just keep rewriting and rewriting, you will never stop to actually publish it. It might be good enough! As I see it, a story isn't truly finished until someone reads it. The objective is for someone to read it (and like it), not to achieve some mythical perfection.
And even perfectionism can work against you! Here's what happened to Dick Lochte's first book: "Each time I'd return to the manuscript, I'd begin by reworking that first chapter. Before long I had a brilliant first chapter, but I'd grown tired of the book."
I'm not saying to give up on high standards, but to finish a book it may be necessary to finish it in some form, and then edit it. You may well see all the flaws, but that doesn't mean the work isn't already quite good!