The worst of doing one’s duty was that it apparently unfitted one for doing anything else.

Wharton’s line captures a paradox at the heart of moral and social obligation: dutifulness can become a kind of specialization that narrows the self. When “duty” is defined externally—by family, class, or convention—performing it well may train a person to suppress desire, spontaneity, and imaginative risk. The speaker’s complaint is not that duty is worthless, but that it can be totalizing: it rewards compliance and steadiness while leaving one ill-prepared for other forms of living (love, ambition, creative work, or even self-knowledge). In Wharton’s world, this is also a critique of societies that prize propriety over vitality, producing people who are morally “correct” yet emotionally and intellectually stunted.