O God and Heavenly Father,
Grant to us the serenity of mind to accept that which cannot be changed; the courage to change that which can be changed, and the wisdom to know the one from the other, through Jesus Christ our Lord, Amen.
–The so-called Serenity Prayer, often attributed to Reinhold Niebuhr and many others (when I first learned it before being a Christian in high school I was told it was by Saint Augustine), but which clearly predates him and whose original authorship is still in some dispute/doubt