Jennifer Garner: I 'Would Do Anything' for Ben Affleck

"We both know we couldn't do what we do without each other," the actress says in the January issue of InStyle, on sale Friday. "Ben always says, 'If you love it, we can make it happen.' "

With Hollywood breakups running rampant, what’s the secret to Jennifer Garner and Ben Affleck‘s successful seven-year relationship?

“We both know we couldn’t do what we do without each other,” the actress says in the January issue of InStyle, on sale Friday. “Ben always says, ‘If you love it, we can make it happen.'”

Of course, jewelry helps, too! Affleck, 39, enjoys showering his wife with diamonds. He gave her a pair of pink and white diamond Harry Winston bands, one for each of their two daughters, Violet, 6, and Seraphina, who turns 3 next month.

“He knows when to swoop in with the gesture. He’s sweet that way,” Garner says. “Honestly, I would do anything for that man, because I know it’s not taken for granted.”

Also not taken for granted is their growing family. The actress, who is expecting their third child this winter, calls pregnancy at age 39 “a game changer.”

Garner admitted to having a difficult first trimester, complete with nausea, exhaustion and junk-food cravings.

“My kids had never seen Doritos before. They would say, ‘Mom, where did you get that orange chip? I really want that,'” she says. “I wish I was one of those cute pregnant girls who wear skinny jeans throughout their pregnancies. 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.”

— Alla Byrne