After years of carefully choosing roles to build their fame in Hollywood, some starlets find themselves playing another role. And that role winds up being their toughest of all — that of a mom.

Motherhood can be a jarring transition for celebrities who jet around the world with all of the money, possessions, and prestige that come with fame. Many come to realize how “selfish” they were in their pre-baby life.

Actress Mila Kunis, parent of 19-month-old daughter Wyatt (her child with Ashton Kutcher), has learned that young ones are oblivious to their parents’ sleep schedule.

“At 6:45 in the morning she’s awake, so so am I. They don’t care that I let loose the night before,” she told the Daily Mail. “I traveled through all my twenties and I was very selfish … in a good way, not in a way I regret. And I think having a kid made me realize how incredibly selfless I want to be. I know that when we decided to have a kid, we were ready to no longer be selfish. Or at least start the process, because innately, as humans, we are really selfish people.”

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Actress Anna Faris said she and her husband, Chris Pratt, had to learn to “live a little less selfishly” to balance career and parenthood after baby son Jack arrived in 2012.

“Everything that everyone says is true. When you’re pregnant you’re like, ‘Yeah, I know. Life is going to change. I never loved anything more. Plan a date night with your husband,'” Faris told The Huffington Post.  “And you hear so much of the same thing, but I really realized after having the child that people really needed to pound the information into you, because it is tidal wave change in your life.”

Faris said she wished she had learned even more from friends ahead of time — for instance, the logistics management required even for small trips outside the home and what it means on a practical level.

“We felt so grateful for so many things, but there is that, ‘Gosh, leaving the house means I’m going to have to pack up all of this stuff for him so I guess I’m just not going to leave the house,'” she said. “I felt myself having the longest conversations about this stuff with people who were probably bored out of their mind talking to me.”

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She had some dull moments as well. “He’s a total ham now, which I love … but the first year of his life was boring,” she said.

Now, he’s three — and she’s a different person.

“Your identity changes,” Faris said. “You are now a mom, sort of the most important job in the world, and the pressure and the guilt and like, all of the things that are sort of wrapped up in that, I don’t think anyone can prepare you for.”

Actress Olivia Wilde called her role as a mother to Otis, her son with Jason Sudeikis, as “the most humbling and adventurous experience.”

“I love watching him sleep because it means you can sleep,” she said.

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Kourtney Kardashian, star of “Keeping Up With the Kardashians,” found herself having trouble keeping a sleep schedule with baby Mason, now six. (She also has daughter Penelope, 3, and baby son Reign.)

“He loved to sleep all day and party all night,” she told Parenting Magazine. “Everyone told me to nap when he napped, but I just couldn’t do it. It was actually a fun time, though.”

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Actress Natalie Portman discovered “how hard it is to be a mother” after her son, Aleph, was born in 2011.

“I never thought of motherhood as being the full-on job that it is. Going to work now feels like a day off,” she told The Telegraph.

Singer Gwen Stefani realized she had to make changes when she became a mother — she and Gavin Rossdale are parents to sons Kingston, Zuma, and Apollo — but at first she wondered what it would do to her career.

“In the beginning, I didn’t want to think of myself as a mother,” she told InStyle. “I was like, ‘Wait a minute! Ain’t no hollaback girl is who I am!’ I had to learn quickly to accept it. Being a mother and having a career — those are just different roles you play. You’re still the same person you were before, but now you’re more because you’re a mother too, with a lot to do.”