This is a common theme for most fairy tales. The good side will be the main character (usually princesses) and the evil side will be the side characters (usually witch, stepmother, stepsister). At the beginning of the story, the evil side will treats the good side badly and as the story comes to an end, the good side will slowly get a happy ending because of its good deeds (helping people, be patience, etc.). Cinderella gets to marry a prince and live a good life at the end of the story because she’s always been patient with her stepmother and stepsisters. To show that Cinderella is really really good, the author writes that Cinderella forgive her stepmother and stepsisters and that she doesn’t have any grunge on them.