Nicole Kidman has love letters from Keith Urban from "every single night" of their romance.

The Australian actress and country musician married in 2006 after being together for a year and now have two daughters together. Their jobs mean they often have to spend time apart, although Keith ensures that doesn't have a bad effect on their relationship.

"For every single night he's away, he leaves me a love letter. Every single night of our relationship," she told the US edition of InStyle magazine. "It keeps us close."

Nicole also spoke of how confident she now feels in herself, something she puts down to Keith and their kids Sunday Rose and Faith Margaret. She knows they all love her for her personality and they've encouraged her to embrace what makes her different to other people - such as her curly red hair.

"I almost never straighten it anymore," she explained. "It's taken me 40-something years, but I embrace the curl. My littlest daughter has the same hair. She likes it when my hair is curly, so I wear it for her."

The 46-year-old star is famed for her slim figure and has given several interviews over the last year which have given people more of an insight into her personality. She knows many think she can be stiff, but insists she is actually pretty relaxed - even when it comes to her diet.

"Keith and I eat at [US fast food outlet] Wendy's," she laughed. "You've got to remember, I'm with a musician on a tour bus. We do drive throughs!"