Final answer:
Jimmy stopped telling dirty jokes because Sara confronted him and asked him to stop, demonstrating the effectiveness of direct communication in setting personal boundaries.
Step-by-step explanation:
The reason behind Jimmy not telling dirty jokes anymore is because Sara confronted Jimmy and asked him to stop. After dealing with the discomfort in silence for some time, Sara made the decision to communicate her feelings directly to Jimmy. By doing so, she set a boundary regarding what kind of communication was acceptable to her.
Once her boundaries were clearly expressed, Jimmy respected her request and ceased telling dirty jokes in her presence. This interaction is a good example of how direct communication can resolve personal conflicts.