Our errors are surely not such awfully solemn things. In a world where we are so certain to incur them in spite of all our caution, a certain lightness of heart seems healthier than this excessive nervousness on their behalf.

William James (1842–1910) American psychologist and philosopher

“The Will to Believe,” sec. 7, New World (Jun 1896)
    (Source)

Originally a lecture for the Philosophical Clubs of Yale and Brown Universities.