Hola. He was hurt so much by his best friend's betrayal, that every time I try discussing it with him he just shuts down.
Aunque cerrarse puede ser más leve. Claro, otros ejemplos con close up: Instead of talking about it, she closes up and does not tell her three best friends; So she closes up, shutting down, refusing to let anyone in. Too scared of being hurt. It's all she's ever known.1