Acting is half shame, half ...

Acting is half shame, half glory. Shame at exhibiting yourself, glory when you can forget yourself.
 John Gielgud

Quotes from the same author

I never accept lengthy film roles nowadays, because I am always so afraid I will die in the middle of shooting and cause such awful problems.
 John Gielgud
One mustn't allow acting to be like stoc kbroker - you must not take it just as a means of earning a living, to go down every day to do a job of work. The big thing is to combine punctuality, efficiency, good nature, obedience, intelligence, and concentration with an unawareness of what is going to happen next, thus keeping yourself available for excitement.
 John Gielgud