Letters 71.37

And when will it be our privilege to despise both kinds of fortune? When will it be our privilege, after all the passions have been subdued and brought under our own control, to utter the words “I have conquered!”? Do you ask me whom I have conquered? Neither the Persians, nor the far-off Medes, nor any warlike race that lies beyond the Dahae; not these, but greed, ambition, and the fear of death that has conquered the conquerors of the world. Farewell.

Seneca, Letters to Lucilius 71.37, translated by Richard Mott Gummere