The only thing in this world that gives orders is balls.
The play is the source, it is orchestrated with words. In a movie, you are not dealing with as much as that. There are machines and wires. When you're acting for a camera, it keeps taking and never giving back.
When you perform with a live audience, the audience comes back to you, so that you and the audience are giving to each other, in a sense. It's an extraordinary thing. It's wild turf up there.