A private journal, and a place for the few things you keep getting wrong. Return to them, revise what you think, and read back, in your own words, whether you are changing.
Put the day down, and leave it there. A quiet page for what happened and what you made of it. Write for a minute or for an hour.
Some things keep happening. Selfishness, jealousy, a short temper. Give each a name. Write what you think causes it and what you will try. When it comes back, return, add what happened, and revise the theory. Earlier versions stay, dated.
The few standards you hold yourself against. Short enough to remember, kept where you will see them.