Learn from your own life. Marcus Aurelius 3.11

Try to take every meaningful experience in your life and digest it to make a rule you live by. Keeping a journal is not about preserving random records, for yourself or posterity, but about trying to focus your attention on memories that matter, so that you become better able to live well, as you learn from them.

Τοῖς δὲ εἰρημένοις παραστήμασιν ἓν ἔτι προσέστω, τὸ ὅρον ἢ ὑπογραφὴν ἀεὶ ποιεῖσθαι τοῦ ὑποπίπτοντος φανταστοῦ, ὥστε αὐτὸ ὁποῖόν ἐστι κατ̓ οὐσίαν, γυμνόν, ὅλον δἰ ὅλων διῃρημένως βλέπειν καὶ τὸ ἴδιον ὄνομα αὐτοῦ καὶ τὰ ὀνόματα ἐκείνων, ἐξ ὧν συνεκρίθη καὶ εἰς ἃ ἀναλυθήσεται, λέγειν παῤ ἑαυτῷ. οὐδὲν γὰρ οὕτως μεγαλοφροσύνης ποιητικόν, ὡς τὸ ἐλέγχειν ὁδῷ καὶ ἀληθείᾳ ἕκαστον τῶν τῷ βίῳ ὑποπιπτόντων δύνασθαι καὶ τὸ ἀεὶ οὕτως εἰς αὐτὰ ὁρᾶν, ὥστε συνεπιβάλλειν ὁποίῳ τινὶ τῷ κόσμῳ ὁποίαν τινὰ τοῦτο χρείαν παρεχόμενον τίνα μὲν ἔχει ἀξίαν ὡς πρὸς τὸ ὅλον, τίνα δὲ ὡς πρὸς τὸν ἄνθρωπον, πολίτην ὄντα πόλεως τῆς ἀνωτάτης, ἧς αἱ λοιπαὶ πόλεις ὥσπερ οἰκίαι εἰσίν. τί ἐστὶ καὶ ἐκ τίνων συγκέκριται καὶ πόσον χρόνον πέφυκε παραμένειν τοῦτο τὸ τὴν φαντασίαν μοι νῦν ποιοῦν καὶ τίνος ἀρετῆς πρὸς αὐτὸ χρεία, οἷον ἡμερότητος, ἀνδρείας, πίστεως, ἀφελείας, αὐταρκείας, τῶν λοιπῶν. διὸ δεῖ ἐφ̓ ἑκάστου λέγειν· τοῦτο μὲν παρὰ θεοῦ ἥκει, τοῦτο δὲ κατὰ τὴν σύλληξιν καὶ τὴν συμμηρυομένην σύγκλωσιν καὶ τὴν τοιαύτην σύντευξίν τε καὶ τύχην, τοῦτο δὲ παρὰ τοῦ συμφύλου καὶ συγγενοῦς καὶ κοινωνοῦ, ἀγνοοῦντος μέντοι ὅ τι αὐτῷ κατὰ φύσιν ἐστίν. ἀλλ̓ ἐγὼ οὐκ ἀγνοῶ· διὰ τοῦτο χρῶμαι αὐτῷ κατὰ τὸν τῆς κοινωνίας φυσικὸν νόμον εὔνως καὶ δικαίως, ἅμα μέντοι τοῦ κατ̓ ἀξίαν ἐν τοῖς μέσοις συστοχάζομαι.

There is one thing I should add to the maxims I repeat to myself: I should create some personal instance or portrait of what each one represents to my imagination, so that I can see it vividly and substantially—examining all its parts separately in my mind's eye, uttering to myself its name and the names of all its components, what knits it together and what will remain when it is unmade. Nothing fosters greatness of mind more than a capacity to measure the events of life with method and truth, looking always to the same standards. The result of this habit is that we consider maxims and experiences in terms of practical use. What does my experience offer the world at any given moment? What is its worth to the whole? What is its worth to a man who belongs to the loftiest city that exists, a city so exalted that other cities are to it as households? What is my experience made of? How long has it been able to occupy my imagination? What virtue is it good for? Courtesy? Courage? Faith? Simplicity? Independence? One of the others? Then I must pronounce judgement on each experience: this one has come from a god, while another arrives from luck, a chance meeting among the threads woven in fate's web. Yet another derives from someone close to me, a kinsman by birth and circumstance, though he be ignorant of his own relationship to nature. For my part, I am not ignorant, so I make proper use of the natural law of shared circumstance in relating to my fellow humans, aiming to strike a balance at once just and kind in all the dealings we share.