Why does Becky break up with the narrator?

Becky breaks up with the narrator because he began to get too serious. When she is younger she thinks that he is no fun anymore, but when she is older she explains that he was getting too deep into their relationship and she did not want to be a home wrecker. Becky is much younger than the narrator, and she still wants fun and excitement. She is not ready for something serious yet, especially with a married man with so much baggage. At first things are light hearted for the narrator, just something fun and meaningless. However, he begins to really feel for Becky and becomes obsessed with the same things that she does. She senses that he is falling in love with her. When he tells her he will leave his family for her, this is the final straw. His behavior scares her and puts her off, and she breaks it off with him before things go too far.