Acting is kind of a forced compassion, where you learn that given certain circumstances, you can feel and do things that you never thought yourself capable of. And so it stops you from being super-judgmental.
I don't like to plan. Very often, for me, acting is like loving; it's using the muscle that you use in loving, in that your heart feels open. Physically, you feel open. And so therefore your job is to enter, open, and listen. And see what happens.
That's one of my little expressions. I never really studied acting so I kind of kiddingly talk about "building your circle" and "mooding up," because I really didn't learn any technique.
In the theater, you're so much more in charge as an actor. For better or for worse, you know what the audience is seeing. But you can be acting your socks off on film, and then you see the movie, and the camera is on the other actor, or they've cut out the lines you thought were significant, or they've adjusted the plot. So much of it is out of your control.