You're working at it all the time. If you've got any kind of feeling about your work at all, about your medium, you're going to try and get the best out of it.
Every scene is something new.
Everything is new. You never shoot the script. A good director always rewrites and is actually a co-writer on the script. They take credit for it now. But you write right up until the time you shoot a picture and put it in the can.