A great deal of talent is lost to the world for want of a little courage. Every day sends to their graves obscure men whose timidity prevented them from making a first effort.

Sydney Smith (1771-1845) English clergyman, essayist, wit

Lecture (1804-1806), Moral Philosophy, No. 9 “On the Conduct of the Understanding,” Royal Institution, London
    (Source)

Collected in Elementary Sketches of Moral Philosophy (1849).