The ending of Go Tell It on the Mountain occurs on the same day the story opens--John's fourteenth birthday. This is a day on which his mother gives him the gift of independent action (if only for a day) and it concludes at a church service. The church service is a special one, a particular one. It is, in part, a "rite of passage" from boyhood to adulthood for John, and it is, in part, a confessional experience with renewal as it's goal for John's family members.
In the service two major things happen. The first is that John has an epiphany--an inner awakening--through which he chooses to yield himself wholeheartedly to God. The young preacher Elisha kisses him on the forehead as a benediction (a pastoral blessing) on his choice and actions.
The second is that according to custom each of John's family members in turn give an audible prayer of confession as a hope for spiritual and personal renewal. This prayer is a means of reviewing the good and wrong of their lives and actions, with the belief that public acknowledgment will pave the road toward making wrongs right and choosing right over wrong.
As a result of listening to each of his family members' prayers, John makes his own prayer, which is to avoid the anger and hatred that is dominating the lives of his family members in one way or another. John has discovered the secrets that are making his family act the way they do; he recognizes the destructive power of the choices they have made. He recognizes that the brutality and cruelty he and his mother experience are the result of the anger and hatred that family members have confessed to. John chooses to form his identity build on the opposites of anger and hatred.