The serenity prayer is based upon the writings of the Greek philosopher Epictetus (A.D. 55 - A.D. 135). Here is a brief quote from wikipedia.com:
"To Epictetus, all external events are determined by fate, and are thus beyond our control, but we can accept whatever happens calmly and dispassionately. Individuals, however, are responsible for their own actions which they can examine and control through rigorous self-discipline. Suffering arises from trying to control what is uncontrollable, or from neglecting what is within our power."
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