This is not at all "how to be a stoic". This is "what it is to be a stoic".

It's nice to say you have to avoid reacting to things outside of your control. But how does one do that ?

Stoicism fails at explaining any practical way of embrassing the teaching. It's strange since they were quite practical people, but you see that a often in philosophy: lots of theory, very few advices for practice.

At least the buddhists suggest meditation as a tool to learn to act instead of reacting, and see things more objectively.