Letters 85.6

If by your definition the wise man has any passions whatever, his reason will be no match for them and will be carried swiftly along, as it were, on a rushing stream,—particularly if you assign to him, not one passion with which he must wrestle, but all the passions. And a throng of such, even though they be moderate, can affect him more than the violence of one powerful passion.

Seneca, Letters to Lucilius 85.6, translated by Richard Mott Gummere