The words and wisdom of Constantin Stanislavski:
It is important to know what you are feeling on the stage, because it often happens that even the most experienced actors work out at home and carry on to the stage something which is neither important nor essential for their parts.
Delicate and deep human feelings . . . call for natural emotions at the very moment in which they appear before you in the flesh. They call for the direct co-operation of nature itself. (AP)