As part of a personal journey, I am returning to a book that has sustained me for decades -- Baltasar Gracian's "The Art of Worldly Wisdom" which consists of 300 aphorisms. I present them here in the order in which they arrive to me when I flip the book open at random.
Gracian's aphorism #50: Never Lose Respect for Yourself: "Never lose respect for yourself. Do not be lax when alone; let the same integrity always be the standard of your conduct, and owe more to the severity of your own opinion than to the precepts of others. Avoid doing anything questionable more from fear of your own judgment than from the rigor of authority or public opinion. Come to fear yourself and there will be no need for Seneca's imaginary tutor."
My interpretation: Seneca said you should philosophically monitor yourself for certain qualities and characteristics, and do so constantly, especially with regard to errors in judgment. Seneca told his student Lucilius to "dispute" with himself. Gracian claims you don't need to do so if you learn to fear your own self-opinion -- that is, to develop it as a habit. The purpose is not to live in fear of yourself but to always put self-respect -- your own self-judgment -- above the opinions of others, and even above your own emotional reactions. A person with self-respect is to envied because he or she also has peace of mind as well as a moral compass and a strong buffer against the world of opinion. Peace of mind has been called "heaven on earth."
A useful tool in monitoring yourself is to keep a journal of your thoughts, judgments and reactions to experiences. I've done so for much of my life and the journals form an invaluable record of errors as well as situations I've handled well. It may sound odd but the younger version of me has often provided comfort and solace to the older version when I read pages from decades ago. It is like rediscovering an old friend. Also strangely, the older version of me sometimes tries to console the younger one by saying or thinking "don't worry, X,Y or Z gets much, much better. Chin up."
" Avoid doing anything questionable..." This is difficult advice to follow. You don't always know what the consequences of your words or actions will be and even prudently chosen ones can bring bad, unintended consequences. This means you should act and speak only when you are reasonably convinced that your words or actions are correct. Then, if there are unintended and unfortunate consequences, you can still sleep at night with the knowledge that you did the best you could with the limited information you had.
One aspect of this advice runs against modern convention. When you are alone, the modern narrative goes, you should let your hair down and let it all hang out. Gracian says you should never stop monitoring yourself. I don't which is the best advice but I suspect it is a mixture of both because, Lord knows, there are times when I feel exhausted and the last thing on earth I want to do is to monitor myself for purity of character. On most occasions, however, it is probably a good idea to do so if only because it forms the habit of being your own moral monitor.