You probably don't think of Trainwreck as a story about a character having an existential crisis, but at the core of Amy's story lies this question: Who are you? Are you promiscuous party girl who is straddled with your father's awful parental commentary: "Monogamy isn't realistic." Or are you an individual capable of moving forward, growing up, and entering into an adult romantic relationship. Throw in questions of career and family, and the story's Protagonist actually has a lot going on in terms of her psychological journey. Simple story. The plot certainly is. We've seen this type of narrative hundreds of times. Girl finds Boy. Girl loses Boy. Girl gets Boy back. Complex characters. Amy and the rest aren't terribly complex. That's all scalable to the type of story it is. This is a comedy so Amy's complexities aren't overbearing. After all, this isn't Shakespeare. But if you read my comments on Characters and Themes, you'll see she DOES have some inner stuff to deal with, just enough to sustain this narrative and balance out the humor with humanity.