ON ACTING: Emotions and Energy
To be deeply 'connected' emotionally to a role or performance takes the highly synergistic working of the inner body (often called emotions), of literally billions of inner neural connections and chemical flows within us passing to and fro. What we call 'feeling' is really the experiencing of inner physical conversations, if you will, between billions of molecules passing information back and forth to one another within us, indicating to multiple portions of our body a most complex and involving set of instructions how to act and react.
The exhilaration felt at the end of her emotionally draining performance is satisfaction: a job well done. It was, as Milton expressed it (at the end of his great tragedy, Samson Agonistes): "with calm of mind, all passion spent."
By being involved in a wonderful performance, the actor's body has been operating as a huge inner and outer machine, working furiously to attain our (the character's) human ends. Little wonder that at the culmination of a deeply emotional operation, the actor is exhausted. The actor has given a wonderful and deep emotional performance and has achieved a personal and public catharsis, a therapeutic release of his/her deep feeling. The actor has experienced deep human involvement (as in a psychiatric experience) in the safe setting of a staged or filmed context. How exhilarating...and exhausting. And needful of a vacation.
That's why actors have to be in physical shape. While we often think of emotions and outer physical expression as two separate entities, they are really one. A great performance is the inner and outer body engaged in an action of supreme physical (inner and outer) involvement. Good acting is a total physical experience.