Sort everything into two bins: what is up to us (our judgments, impulses, desires, aversions, our own acts) and what is not (body, property, reputation, office, the acts of others). Invest desire and aversion only in the first bin, because those things are by nature free and unobstructed, while treating the second as not yours to command prevents frustration, blame, and the sense of being thwarted.
People are disturbed not by things themselves but by their opinions about those things; death, for instance, is not terrible, since otherwise it would have seemed so to Socrates, but the judgment that death is terrible is what frightens. Therefore when obstructed or distressed, direct blame inward at your own beliefs rather than outward at circumstances or other people.
Regard yourself as an actor in a play whose length and casting (beggar, cripple, ruler, private person) are chosen by someone else; your only task is to play well whatever part is given, not to select the part. Applied to possessions and loved ones, this means saying not 'I have lost it' but 'I have given it back,' since what you held was never owned but merely lent.