What metaphors are used in A Life in the Theatre by David Mamet?

In an essay about the play, Mamet quotes Camus as saying that the actor's task "is a prime example of the Sisyphean nature of life." Even as that metaphorical rock begins to roll backward, the actor doggedly continues with the struggle. Further he notes how "a life in the theater need not be an analogue to 'life.' It is life."