Michel Foucault writes extensively on the care of the self, and how practices of the self have manifested historically. One point driving Foucault’s genealogy of that care of the self (prior to the Cartesian moment, but then resumed by psychoanalysis) is the undergoing of a transformation of the subject in relation to truth. To take care of the self is to undergo change, to reform oneself, and to be constantly engaged with the self in order to truly have access to oneself. Taking care of the self is then in part discovering the self, which is to be done through transformation of who it is that you are–a transformation that does not cease until you cease, a transformation that is living itself, so that taking care of the self is essentially learning how to live.
For the Stoics, it is more like learning how to die. Care of the self, for Seneca, is the striving for a continuous movement toward old age. This is not a chronological old age that he has in mind, but an ideal old age. In Foucault’s interpretation, it is about placing oneself in the condition to live as if life is already over–to assume the detachment of someone who has already completed her life. Further, as Foucault deduces about the fundamental themes of practices of the self among the Stoics, there is a notion of unlearning: “to become again what we never were.” In tending to the self, a subject learns how to empty herself of the “they,” and of the grip of troubles that come mostly from being part of a world, and being too preoccupied with things beyond the control of the self.
The Stoics are notorious for prescriptions of this sort. Below is some advice from Seneca, found in Volume I of the Epistles, on the topic of travel as a cure for discontent. It makes minor mention of the transformation Foucault focuses on, although here it is proposed more like a correction-liberation. Correction, though popular among Stoics, is later revived and institutionalized with the emergence of psychiatry, which Foucault discusses at length in Madness and Civilization, and the prison, which he discusses in Discipline and Punish.
So, says Seneca:
“‘The knowledge of sin is the beginning of salvation.’ This saying of Epicurus seems to me to be a noble one. For he who does not know that he has sinned does not desire correction; you must discover yourself in the wrong before you can reform yourself. Some boast of their faults. Do you think that the man has any thought of mending his ways who counts over his vices as if they were virtues? Therefore, as far as possible, prove yourself guilty, hunt up charges against yourself; play the part, first of accuser, then of judge, last of intercessor. At times be harsh with yourself. Farewell.”