How one should be in both body and soul when overtaken by death; the shortness of life; the immensity of time future and past; the feebleness of all things material.
Look at causation stripped bare of its covers; look at the ulterior reference of any action. Consider, what is pain? What is pleasure? What is death? What is fame? Who is not himself the cause of his own unrest? Reflect how no one is hampered by any other; and that all is as thinking makes it so.
The model for the application of your principles is the boxer rather than the gladiator. The gladiator puts down or takes up the sword he uses, but the boxer always has his hands and needs only to clench them into fists.
In these four chapters, there seems to be a common theme and the first word in chapter 6 is the key: practice. I am thankful for philosophers and practitioners of philosophy who have gone before me. They have spelled out the logic of Stoicism and have expressed how best to put that philosophy into practice. Life is practice, whether trying to master a technical task or a philosophical one.
We ought to practice remembering the shortness of life as often as we can. In contrast to our short life stands "the immensity of time future and past" and in that vast time, how all material things vanish.
We ought to practice breaking everything into parts (discipline of assent). We ought to really think about what these things, (such as pain, pleasure, death and fame) mean. They are out of our control, so they mean nothing, What truly matters is our opinion and our focus on becoming courageous, temperate, just and wise. These are the things that are in our control.
And when should be practice? Always. Like a boxer who is always ready, who doesn't require the need to get a weapon, for his weapons are a part of him already.
(see also Citadel p. 38, 40, 166-167, 272-273)