Keith Urban, People MagazineKeith Urban is featured on the cover of the new country issue of PEOPLE magazine, and inside he reveals his wife's love changed him ... for the better.

"It's been a profound impact [on my songwriting] to meet somebody who offered me a life and helped me become the person I wanted to be," Keith explains. "I felt the power of love in all its phases. There was an expansion of color and joy."

Keith and actress Nicole Kidman met at an Australian Awards event in 2005 and began a whirlwind courtship, eventually tying the knot in June 2006.

The singer-songwriter says Nicole's influence is quite literal, case in point the song 'My Heart is Open,' which is from his 'Defying Gravity' album. "My wife and I had been out a couple of times and I wondered how she felt about me," Keith says. "It came out as, 'How is your heart?' She said, 'It's open.' My God, what a beautiful answer."

Nicole stood by her man when he voluntarily entered rehab at the Betty Ford Center for his alcohol addiction just a few months after their wedding, and the saucy Aussie says his wife's unfailing support and the birth of their daughter Sunday Rose in 2008 has opened him up more than he thought possible.

Keith's wife is so devoted to her husband and children and says she's prepared to leave her career behind for the sake of her family. "I've worked since I was 14 ... but now my priority is my family -- my baby, my husband -- and that's non-negotiable," Nicole tells SHE magazine. "I'm not going on location unless we all together. I've worked hard enough -- and now it's all about resting and enjoying."

Nicole and Keith are never apart for more than a few days, and when they're not together, they make sure they leave reminders of their love for one another. "Keith and I never text or email -- we write letters to each other," Nicole reveals. "We slip them in each other's luggage and he hides them in my bag, leaves them under my pillow."

There are a lot of different feelings and emotions Keith will be putting into writing songs for his new album, which he's working on for the next few months. Daughter Sunday may be a whole new inspiration for him. He says that she's already given him "a new joy, a new sense of purpose." And for a guy whose sole purpose was to make music and play guitar just a few short years ago, he has certainly turned into the man he wanted to be and who we knew he was all along.