APA Style

McGonigal, K. (2012). The willpower instinct : how self-control works, why it matters, and what you can do to get more of it . : Avery.

MLA Style

McGonigal, Kelly. "The willpower instinct : how self-control works, why it matters, and what you can do to get more of it". : Avery, 2012. BOOK.