Reinhold Niebuhr, The Serenity Prayer (ca. 1942). This statement, or variants of it, have often been attributed to others, including St. Francis of Assisi, but without sources. Though similar prayers may have existed, the work seems to be Niebuhr's. He never copyrighted the prayer, and it has been used in many variants, including the most common variant: "God grant me the serenity to accept the things I cannot change, courage to change the things I can, and the wisdom to know the difference".https://en.wikiquote.org/wiki/Serenity