Cameron Diaz Talks 'Surprise' Marriage to Benji Madden: 'I Didn't Think It Was Something I'd Do'

Getty Images

Married is not something Cameron Diaz necessarily expected to call herself.

The 43-year-old actress, who wed 37-year-old Good Charlotte rocker Benji Madden in January 2015, opens up to Harper's Bazaar about her matrimony, admitting it was a "surprise."

"That was the biggest thing I've done in my 40s, and it opened me up in different ways," she reveals. "It's pretty awesome. I didn't think it was something I'd do, and I don't know if I'd have done it if I hadn't met my husband."

WATCH: Cameron Diaz Opens Up About Her Marriage to Benji Madden on ‘Ellen’: ‘I Couldn’t Do It Without My Husband’

Diaz addresses how entering her 40s has changed her, saying it's a big focus in her new book, "The Longevity Book."

"As you get older, your body changes in so many little ways. It doesn’t react the same way it used to, I don’t get the results that I used to as easily as I once did," she says, adding: "Just like everyone else, I’m more and less disciplined at various times based on what’s going on in my life."

WATCH: Cameron Diaz Pens Heartfelt Note to Benji Madden: ‘I Never Knew What Love Was Until I Found You’

With that being said, Diaz doesn't believe you should let a number rule your life.

"Everybody’s age is different and by that I mean that even when you’re a certain age, it’s all a matter of how you present yourself, how old your spirit is, and where you are in your life," she says. "Some 50-year-olds are still 35. It’s about expression and what they can pull off."

Watch the video below for more of Diaz's thoughts on marriage.