The Stoics were not theorists of philosophy. They were practitioners of a discipline, and that discipline had a shape over the course of a day. The shape is unembarrassed about being a routine. The Stoic day has three movements: a morning preparation, sustained attention through the day, an evening review.
Morning — preparing the assent
Marcus Aurelius opens Book Two of Meditations with the passage everyone half-remembers:
Begin the morning by saying to thyself, I shall meet with the busybody, the ungrateful, arrogant, deceitful, envious, unsocial. All these things happen to them by reason of their ignorance of what is good and evil.
This is not pessimism, and it is not bracing oneself. It is rehearsal. The Stoics called it praemeditatio malorum — the premeditation of possible difficulties — and they did it on purpose, before the day made its first demand. Naming, in advance, what might go wrong removes the surprise. The thing, when it arrives, has already been met once. The day then begins with no debt.
Through the day — prosoche
The Stoics used the Greek word prosoche — attention, vigilance — for the sustained mental posture that ran underneath the day. It is the discipline of catching, in real time, the moment when an impression arrives and asking what to do with it. Epictetus is direct about the technique:
It is not the things themselves that disturb people, but their judgements about those things.
The dichotomy of control is the question that closes the loop. Of the thing that has just landed — the email, the delay, the comment, the headache — what is mine, and what is not? Act on what is mine. Drop what is not. The Stoics expected this to be the work of a lifetime, not a Tuesday. Marcus, who was the emperor, reminds himself dozens of times.
Evening — the review
Seneca, in the third book of On Anger, describes the practice he learned from the philosopher Sextius:
When the light has been taken away and my wife has fallen silent, aware of this habit that's now mine, I examine my entire day, going through what I've done and said. I hide nothing from myself, pass over nothing.
The evening review is honest accounting, not self-flagellation. What did I do well today? Where did I fall short? What will I do differently tomorrow? The questions are concrete; the answers are short. Done daily, the review builds the muscle the day requires — the ability to see oneself clearly, without either flattery or contempt.
What this is not
The modern self-help compression turns this into a productivity stack — wake at five, journal, cold plunge, lift, hustle. That is not what the Stoics did. There is no record of any of them in a cold plunge, and no Stoic text recommends 5am. Marcus actually complains, in Book Five, about the difficulty of getting out of bed. Seneca was rich and lived well. Epictetus, who had been a slave, taught for free in a borrowed building. The Stoics were not optimising. They were practising attention, in lives that often did not look enviable from the outside.
The school is portable because the practices are portable. A morning rehearsal of the day's difficulties. Attention to the gap between what happens and what you do with it. An honest evening review. Done unsensationally, for years, this is what produced the texts you have heard of.