Lori Berenson has always loved to walk. When she was a high-school student in Manhattan in the mid-1980s, she walked home at night from her job at Pasta & Cheese, on the Upper East Side, to the apartment where she grew up, on East 25th Street. When she began her prison sentence in Peru, in 1996, for collaborating with a terrorist group, convicted terrorists had to spend 23½ hours a day inside their cells. Even then, Berenson walked in the 6-by-9-foot space she and another woman shared — two steps forward, two steps backward — for hours. “People ask, what did you miss most?” she said in August, two and a half months after she was released on parole, having served nearly 15 years of a 20-year sentence. “This was definitely it.”