Jennifer Garner is InStyle’s January cover girl! In this issue, the actress, producer, and soon-to-be mom of three clues us in to her secret to happiness (and sanity). One key element—her support system, husband Ben Affleck. “I don’t know how or why it works as well as it does,” Garner says of her relationship. “Honestly, I would do anything for that man, because I know it’s not taken for granted,” she adds. And their family is growing—daughters Seraphina and Violet will get another sibling any minute now. “I wish I was one of those cute pregnant girls who wear skinny jeans throughout their pregnancies,” says Garner. “But I just gain weight. I’m trying really hard to be mindful, but when I’m making the kids mac and cheese, I want it badly.” As for where you’ll see her next, check out Butter, a movie she produced and stars in, hitting theaters in 2012. “I identified with her loss of identity,” she says of her character. “You identify with your career then become a mom and put everything you have into the happiness of those kids. And though I wouldn’t change it for anything, you lose part of yourself.” For more of our exclusive interview with Jennifer Garner, pick up the new January issue of InStyle, on newsstands Friday.

Cover: Donna Karan Casual Luxe sweater coat. Photo: Vionnet silk dress, Kara by Kara Ross earrings, Lanvin bracelet, Salvatore Ferragamo wedges.

Plus, see how Jennifer went from high school sweetheart to stunning red carpet star in the gallery! 

Jen's Transformation!

MORE:
• Jennifer’s Hottest Red Carpet Looks!
• Try on Jennifer Garner’s Hairstyle!
How Jennifer and More Dress Their Baby Bumps
• Hollywood’s Hottest Moms
• The Latest InStyle Cover Girls