Men are not prisoners of fate, but prisoners of their own minds.

The line contrasts external determinism (“fate”) with internal constraint (“their own minds”), arguing that what most limits people is not circumstance but fear, habit, and self-imposed beliefs. Read this way, it is a call to psychological agency: changing one’s outlook can expand the range of possible actions even when conditions are harsh. The aphorism resonates with themes common in modern motivational rhetoric—especially in eras of crisis—because it reframes adversity as partly a problem of perception and courage. However, without a verified Roosevelt context, it should be treated as a general maxim rather than securely tied to a specific policy moment or speech.