Meditations 5.23-24:

23. Keep in mind how fast things pass by and are gone—those that are now, and those to come. Existence flows past us like a river: the “what” is in constant flux, the “why” has a thousand variations. Nothing is stable, not even what’s right here. The infinity of past and future gapes before us—a chasm whose depths we cannot see.
So it would take an idiot to feel self-importance or distress. Or any indignation, either. As if the things that irritate us lasted.
24. Remember:
Matter. How tiny your share of it.
Time. How brief and fleeting your allotment of it.
Fate. How small a role you play in it.