Brad Paisley and Kimberly Williams-Paisley are sharing the secret to their happy 18-year marriage. In a recent interview with People, Kimberly says that she and Brad keep a journal of their special moments. "Our greates hits," she shares. "We record the meaningful moments, the best laughs. That's a big part of our relationship...focusing on the laughter and keeping a sense of play." The couple are on the cover of the newest issue of People magazine, which is available on Friday.