I don’t want them to change me in there. Turn me into some kind of monster that I’m not.

Peeta knows that he likely won’t survive the Hunger Games; what he’s more concerned with is making sure the traumatic experience of the Games does not irrevocably change him. Thus far, Peeta has shown himself to be a genuinely good person – the type of person willing to take a beating to save another’s life. But he knows that this goodness may break down and even be replaced with cruelty when he faces the brutality of the Games. Peeta is ultimately struggling to reconcile how he can hold onto his identity and personhood in a society that forces you to forego your humanity to survive.

Don’t die for me. You won’t be doing me any favors.

Throughout their time in the arena, both Peeta and Katniss admit that they would rather the other survive. For Peeta, Katniss seems a more deserving victor. Her family’s poverty is more severe than Peeta’s, and their lives would be vastly improved if Katniss won the Games. Furthermore, he believes that Katniss would be missed more than he should she perish in the arena. Katniss is the breadwinner and protector of her family, whereas Peeta feels less valuable in a family with many siblings. Overall, Peeta sees Katniss's life and future as full of purpose and necessity, unlike his own. And his romantic feelings for her also cause him to value her life over his. He has no interest in going home without her.

It was all for the games. How you acted.

While much of the romance between Katniss and Peeta is fabricated on Katniss’s part, for Peeta, it’s genuine. Peeta enters the Games already harboring feelings for Katniss, and later admits that he’s been interested in her since their childhood. Peeta doesn’t realize that Katniss’s romantic actions toward him in the arena were a strategy to gain support and resources from sponsors. After the trauma they endured together, and how close they grew as they protected each other in the arena, this is a devastating betrayal for Peeta, who likely believed their relationship would continue post-Games.