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.
Marcus Aurelius (2002). “Meditations: A New Translation”, p.61, Modern Library
