MA>I read this in a book on writing Science Fiction and Fantasy 
MA>(Which does qualify for most of the stories on this list, even if they 
MA>are not totally dedicated to either.)

As a Fantasy Fan first and Anime Fan second, I can only
hope that this is good advice! ^_^

MA>immediately.  Things you don't like about the story.  You'll be tempted 
MA>to go back, reediting the story to correct those mistakes.  DON'T!  Spend 
MA>your time writing new material, not fixing the old stuff.. or you'll 
MA>never get anything new accomplished.  

I follow this model myself. Personally, it's because I'm too
lazy to fix it up ^_^ but practically, it's because I want
to get on with the rest of the story. I write slow enough
as it is.

MA>Rely on continuously writing new stuff to improve your skills.

Unless it was just a draft, I usually don't rewrite my work.
This does not mean that I don't care for the valued C&C 
which readers sent in, but that I'd rather apply that C&C
later on in the fic. If that's not possible, well, then I'll
apply it to the next fic.

Who cares if your work isn't perfect? Personally, I write
for fun, not for perfection. While it's nice to have a really
good fic out on a golden pedestal, it's too much of a
waste for someone such as myself who writes slow enough
as it is but has a ton of ideas cascading in his head.