Once the camera starts rolling

You'd begin to realise how you're saying things THROUGH it.

The meanings of frames and images change - they transform into a sort of language, they begin to tell a story just the way you wanted.
And that, is not something you had imagined when you were writing the scripts or working on the storyboard.
You just thought it's how the story should be going, how the video is played in you mind.
You thought you were copying the images flowing in you head, just because they feel natural after 20 years of watching films in a squared box.
And yet, once you wave the people into action, everything starts to fall into place, showing the real power you hold in your hand: not that you get to yell people around, but the power to decide which viewpoint the audience is going to have.
You hold the key to this framed world, and in this world, they will believe whatever you want them to believe.
And that's the moment you get a slight taste of this magical job, of being a director.