After you finish a draft, you will defend everything in the script as if it were life or death.
This is why you must wait until:
First...there is a spectrum:
Defense----------------------------------------------Offense
When you finish a first draft you will be on the far left:
Defense-[]------------------------------------------Offense
You need to wait until you are, ideally, halfway between the two:
Defense----------------------[]--------------------Offense
How long does this take?
3 to 6 months at least,
