Analysis of O had I known that thus it happens...

O had I known that thus it happens,
When first I started, that at will
Your lines with blood in them destroy you,
Roll up into your throat and kill,

My answer to this kind of joking
Had been a most decisive 'no'.
So distant was the start, so timid
The first approach-what could one know?

But older age is Rome, demanding
From actors not a gaudy blend
Of props and reading, but in earnest
A tragedy, with tragic end.

A slave is sent to the arena
When feeling has produced a line.
Tnen breathing soil and fate take over
And art has done and must resign.