Peeta experiences the extremes of behavior conditioning in Suzanne Collins' novel Mockingjay. 

Peeta undergoes the largest transformation at the hands of the Capitol when they "highjack" him, a "secretive...form of torture" that is a "type of fear conditioning" (180).  Prim asks the question that had been plaguing Katniss' mind:

"Is that what they've done to Peeta? Taken his memories of Katniss and distorted them so they're scary?" (181)

Although Katniss and Prim both want rehabilitation for Peeta, it is Delly, their classmate from District 12, who comes up with the solution to restore Peeta's mind.  In what becomes a reverse-highjacking, Delly works with Peeta to help him connect to his good childhood memories and understand what is real in the world around him. 

When Peeta states that he "can't tell what's real anymore and what's made up," Finnick advises him just to ask.  In a game that becomes "Real or not real?"  Peeta attempts to decipher his feelings and nightmares. 

Peeta's personal fortitude and the aid of those closest to him, like Delly, Haymitch, and Katniss, help Peeta to overcome his reconditioning and redefine himself for the future.