New mother Kate Winslet has another reason to celebrate: She has kicked her caffeine and nicotine habits! The two-time Oscar nominee — who gave birth to her first child, daughter Mia, last month — tells TV Guide Online she no longer needs the dual vices now that she's a mum.

"I'm much calmer," the Titanic actress admits. "I feel like a different person. When I was in a stressful situation, like doing interviews, I'd be running out for a cigarette and drinking endless cups of black coffee. Now I don't smoke anymore and I'm still totally relaxed."

Winslet, who reports that her husband, director Jim Threapleton, also is adapting smoothly to his new role as father, still can't quite get over the miracle that is child birth. "It feels like the most natural thing in the world," she marvels. "It's brilliant. But I still can't quite believe I'm a mommy.

"I had 30 hours of labor," she continues, "but if they told me I had to endure 30 more, I would have done it in a second — just to have a look at her."

Well, Mia will likely be well into her teens before she's allowed to see her mother's latest film, the erotically charged Quills. Opening in limited release on Nov. 22, the offbeat pic stars Geoffrey Rush as infamous sexual maven, the Marquis de Sade. "It's very dark and sort of weird," admits Winslet, who plays de Sade's maid. "I had to do a very shocking scene with Joaquin Phoenix. It was very difficult for both of us emotionally, and even more difficult for me because I was naked. I was very lucky that Joaquin has incredible respect for women... I felt comfortable with him."

Winslet also felt at ease with Oscar-winner Rush. "Geoffrey is the naughtiest, wickedest actor I've ever worked with," she laughs. "He will happily make his fellow actors laugh in the middle of an emotional scene. There were moments when we were all laughing so much we had to sit down and take a breather.

"We all behaved so badly," she adds, "but it worked because it helped us get through some of the things we had to do on camera."