Most actors make themselves ...

Most actors make themselves unhappy by searching for their sanity, by insisting on their normalcy; it's a grave mistake.
 Michael Shurtleff

Quotes from the same author

Whatever you decide is your motivation in the scene, the opposite of that is also true and should be in it.
 Michael Shurtleff
Competition [in a scene] is healthy. Competition is life. Yet most actors refuse to acknowledge this. They don't want to compete. They want to get along. And they are therefore not first-rate actors.
 Michael Shurtleff
Competition is healthy. Competition is life. Yet most actors refuse to acknowledge this. They don't want to compete. They want to get along. And they are therefore not first-rate actors. The good actor is the one who competes, willingly, who enjoys competing. An actor must compete, or die...Peacefulness and the avoidance of trouble won't help in his acting. It is just the opposite he must seek.
 Michael Shurtleff
Take nothing for granted. Make an emotional discovery as often as you can find one in every scene. Ask yourself: What is new?
 Michael Shurtleff
There's only one reason why a character drinks: to seek confrontation. To fight for what they want in ways normally denied them.
 Michael Shurtleff