Objective judgement, now at this very moment,
Unselfish action, now at this very moment,
Willing acceptance, now at this very moment, of all external events.
That is all you need.
To me that captures the three disciplines (perception, action, will) very nicely. It tells you how to see the world, how to act in the world, and how to come to terms with the world. It is indeed all one needs. You could spend a lifetime trying to just live that quote.
Understanding Stoic Philosophy may help you as an investor maintain rationality, control unwanted emotional reactions, and develop clear thinking for better choices which is, after all, what investing is all about.
The essense of philosophy is that we should live so that our happiness depends on as little as possible on external causes. –Epictetus
Stoicism in six minutes