Don’t mistake your assumptions for the truth. - Epictetus

Say to yourself each time, 'He did what he believed was right.'

"Be careful to leave your sons [and daughters] well instructed rather than rich, for the hopes of the instructed are better than the wealth of the ignorant."
[in brackets: though I have only sons, I am — of course — someone's daughter]

Continually remind yourself that you are a mortal being, and someday will die. This will inspire you not to waste precious time in fruitless activities, like stewing over grievances and striving after possessions.