Or for a lighter read altogether, Tom Wolfe's "A Man in Full"!
Yes I was going to mention "A Man in Full" but you beat me too it. Really an excellent read.
Re translations of Epictetus: these are a bit of an issue. I actually like Sharon Lebell's "adaptation" which takes some translation liberties but gets the gist right and is much easier to read than the more classical (and stuffy) translations. To get the most out of it of course one should read a couple of different translations and see the differences.
I came to Epictetus when I read James Stockdale's biography and the story of his years in the Hanoi Hilton where as the senior ranking officer he was responsible for establishing a code of ethics for the captive American pilots, and he based this on Epictetus. When I saw that I thought it was worth reading since it had to be a robust and accessible philosophy. I was not disappointed .
The reason Epictetus is useful for traders is his emphasis on personal responsibility, awareness, elimination of illusion, disregard of outside opinion, self reliance, etc... all the things that help a trader's mental state.