In film, you're so much in the hands and at the mercy of the editor, so sometimes it's good to watch it just to see how it turns out - it can be so different than how you imagined it. But sometimes it's better to just let it go for your own sense of self worth.
I've learned 90 percent of what I know from watching and listening to actors. A good leading actor is the rock of the show. Their energy and their tone really sets the groundwork for how everything is going to work. I've been lucky to deal with stars who are very giving and generous.