You will always find those who think they know what is your duty better than you know it.

Ralph Waldo Emerson (1803-1882) American essayist, lecturer, poet

Essay (1841), “Self-Reliance,” Essays: First Series, No. 2
    (Source)

This essay was inspired by his reading of Walter Savage Landor in 1833, with passages pulled from his lecture "Individualism," last in his course on "The Philosophy of History" (1836–1837), with other passages from the lectures "School," "Genius," and "Duty" in his course on "Human Life" (1838–1839).