I finally remembered the story and the meaning of dependency on talismans (witchcraft) and the obstacles, temptations and, secrets sins that weigh and wear down a person's conscience into that self-centered joyless, empty path. Choosing truth, honor, courage even though they lead to death you can face any trial righteous. The movie needed more information for an audience that has not read the tale. The Green Knight meant that Sir Gawain had seen there were worse things than self preservation (the green sash) at all costs. He was truly brave by facing the Green Knight honestly and was therefore free to go off With his head.