William Miller, Ph.D., is a clinical psychologist and a professor of psychology and psychiatry at the University of Mexico. He's also the co-founder of motivational interviewing, a strategy therapists use to help people deal with the ambivalence they feel about change. He’s the author of many books, including his most recent book, On Second Thought, which explores the subject of ambivalence. Some of the things he talks about are how to accept that you're not completely committed to change, how to handle mistakes and setbacks, and how to talk yourself into doing something when you're "on the fence."