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.