Why does Joan want to start a new life in the novel, Lady Oracle?

Joan wants to start a new life because it was too complicated to live a double life as Arthur's wife and her secret identity as the romance novelist, Louise Delacourt. Joan cannot share her other life with Arthur, nor has she told him the truth about her past, including her unhappy childhood and weight trouble. When a reporter unearths her true identity, it is too much for Joan and she escapes.