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Marcus writes only in order to have the dogmas and rules of life always present to his mind. He is thus following the advice of Epictetus, who, after having set forth the distinction between what does and does not depend on us - the fundamental dogma of Stoicism - adds:

It is about this that philosophers ought to meditate; this is what they should write down every day, and it should be the subject of their exercises

You must have these principles at hand both night and day; you must write them down; you must read them.

The Stoic philosophical life consists essentially in mastering one's inner discourse. Everything in in an individual's life depends on how he represents things to himself.