The moment you doubt whether you can fly, you cease for ever to be able to do it.

This line is associated with J. M. Barrie’s Peter Pan mythology, where flight functions as both a literal marvel and a symbol of childhood’s imaginative confidence. In the story-world, Peter and the Darling children can fly only when they sustain the right mental state—belief, lightness of spirit, and freedom from self-consciousness. The remark is typically presented as a narrator-like generalization about the rules of Neverland rather than as a historically documented aphorism Barrie delivered in a speech or letter. It crystallizes the theme that growing up brings doubt and rational inhibition, which in Barrie’s fantasy has immediate, physical consequences.

“Flying” functions as a metaphor for any extraordinary ability that depends on conviction, play, and imaginative freedom. Barrie suggests that doubt is not merely an emotion but a disabling act: the instant one questions one’s capacity, the capacity itself evaporates. In the Peter Pan context, this dramatizes the fragility of childhood magic—belief must be continuous and unbroken. More broadly, the line captures a psychological truth about performance and aspiration: confidence can be self-fulfilling, while self-doubt can become self-sabotage. The absolutist phrasing (“for ever”) heightens the warning, implying that once cynicism takes hold, it is difficult to recover the earlier state of effortless possibility.

1) “The moment you doubt whether you can fly, you cease forever to be able to do it.”
2) “Once you doubt you can fly, you’ll never be able to.”