Gwen Stefani: It's a miracle I'm still married to Gavin Rossdale

More than a decade of marriage is not an easy feat -- especially for two people as busy as Gwen Stefani and her rocker husband Gavin Rossdale.

The couple, married for 12 years, have three children together and are constantly battling to balance their work, family time and "me" time.

"We go through so much together — it's a miracle that we could stay together this long," Stefani, 45, told Cosmopolitan. "[Gavin's] on a short tour right now, and he wrote me the sweetest note this morning. It's good to have those days when we both do our own things. I think that's what keeps relationships going, when both people can be themselves and have their own individuality. That's especially important for women. It's hard to find time for yourself."

PHOTOS: Celebrity couples — then and now

Despite Stefani's seemingly rock 'n' roll lifestyle, she said she's shocked to have landed a "hot guy" like her hubby.

"I don't know if I was a nerd in high school, but I definitely wasn't the super-cute cheerleader, so I never saw myself getting somebody like that," she explains. "But I do think he's quite handsome. It's not the most important thing about him, but it is nice — and he makes really cute babies!"

The "Rich Girl" singer married the Bush frontman in 2002 and are parents to Kingston, 8, Zuma, 6, and Apollo, almost 1 year.

WATCH: Reese Witherspoon: Divorce hurt my career