The Canterbury Tales is not a single tale, but a collection of them and each has its own moral lesson. To answer your question in a truly helpful manner I would need to know which tale it is that you are referring to. I would highly recommend looking at the various resources Enotes has on the Canterbury Tales. Specifically the “Themes” page may be helpful to you as it addresses several reoccurring ideas and morals in the stories. Also, if you want to let me know specifically what tale it is you are referring to I can be of more help. Best of luck!