Why is it so hard to break bad habits and replace them with good ones? You may think it all comes down to willpower. But social psychologist Wendy Wood says that if you really want to change your life, then you need to tap into your unconscious mind. Wood, who’s just written a book called “Good Habits, Bad Habits,” chats with Next Big Idea Club curator Adam Grant about harnessing the science of habit formation to make positive changes that last.