The Serenity Prayer is said at just about every 12-step meeting. There are differing opinions as to where it originated.  Most people credit Reinhold Niebuhr.  This is an excerpt from a New York Times article published in 2008:

“The precise origins of the Serenity Prayer have always been wrapped in a fog. Even in Niebuhr’s lifetime, his authorship was challenged. His response was typically modest. He was quoted in a magazine article in 1950 as saying: “Of course, it may have been spooking around for years, even centuries, but I don’t think so. I honestly do believe that I wrote it myself.”

The version of events most often cited in biographies of the theologian is that after Niebuhr used the prayer in a sermon in rural Massachusetts, a neighbor who was an Episcopal priest asked for permission to print it in a booklet for the armed forces in 1944. The U.S.O. distributed it widely.”