6 ideas
Divide everything into what is up to you (your judgments, desires, aversions, and actions) and what is not (your body, reputation, property, and other people). Invest your emotional stake only in the first category, treating the second as borrowed and outside your jurisdiction, and you become immune to frustration and disappointment.
It is not things themselves that upset people but their opinions about those things — death is not terrible, but the judgment that death is terrible is what produces fear. Because the disturbance lives in the interpretation rather than the external fact, you can dissolve distress by examining and revising the judgment.
Never say of anything 'I have lost it,' only 'I have given it back' — your child, spouse, and possessions are returned to the source that lent them, not stolen from you. Holding things as on loan rather than as property removes the sense of injury when they depart.
When a vivid impression arrives, pause and say 'You are just an impression and not at all what you appear to be,' then examine it against the standard of whether it concerns things in your control. This interval between stimulus and assent is where freedom operates, preventing reflexive reactions from becoming convictions.
Remember you are an actor in a play whose length and character are chosen by another — your task is only to perform well the role assigned, whether beggar or ruler, not to select the role. This reframes circumstance as casting rather than injustice, shifting attention from what you got to how you play it.
Don't explain your philosophy — embody it; sheep don't vomit up grass to show the shepherds how much they ate, they digest it and produce wool and milk. The mark of someone making progress is that they blame and praise no one, make no claims for themselves, and watch only their own faults.