In Geoffrey Chaucer's "The Canterbury Tales", the collection of stories were told by the pilgrims to pass their time during their journey to Canterbury. this collection of stories narrated by the different personalities and about differing themes all come together to form the "Tales".
In "The Monk's Tale", he talked about numerous short stories all regarding fortune and how man cannot control how it turns. Taking an example of Biblical as well as historical heroes, he showed how the tragic fortune of these characters turned from great to worse. Be it Satan (a former angel), Adam (former resident of Paradise), Samson (a strong man), Hercules (a great warrior), King Nebuchadnezzar (King of Babylon) all had their fortunes flipped due to their acts of ignorance and pride in themselves. So, the monk showed how fortune is controlled by God and man has no say in what or how it turns.