God, give us the grace to accept with serenity the things which cannot be changed, courage to change the things which should be changed, and the wisdom to distinguish the one from the other.

Reinhold Niebuhr (1892-1971) American theologian and clergyman

“The Serenity Prayer” (1934)

Niebuhr at one point claimed authorship (and took copyright fees from Hallmark Cards), but later on denied he had written it. It was later adopted by Alcoholics Anonymous. Discussion of the actual authorship here.