Letters 66.36

But there are certain goods which reason regards as primary, to which she addresses herself purposely; these are, for example, victory, good children, and the welfare of one’s country. Certain others she regards as secondary; these become manifest only in adversity,—for example, equanimity in enduring severe illness or exile. Certain goods are indifferent; these are no more according to nature than contrary to nature, as, for example, a discreet gait and a sedate posture in a chair. For sitting is an act that is not less according to nature than standing or walking.

Seneca, Letters to Lucilius 66.36, translated by Richard Mott Gummere