The words and wisdom of Constantin Stanislavski:
You may play well or you may play badly; the important thing is that you should play truly (Shchepkin to Shumski).
To play truly means to be right, logical, coherent, to think, strive, feel and act in unison with your role.
If you take all these internal processes and adapt them to the spiritual and physical life of the person you are representing, we call that living the part. This is of supreme significance in creative work. (AP)