Two piees of advice about writing in general :
Compose in Fire
Re-write in Ice.
Just write, write, write, keep writing until you have dissapated the passion and said all you want.
Then, re-write (edit) in a dispassionate, cool-eyed way until you feel it's the best you can do.

And as one great editor said to me after watching me when I was struggling over a story .... "When you come to a good place to stop, for God's sake STOP!"