Laura Linney, 57, says after welcoming her son Bennett Armistead in 2014, she began changing in ways she never expected.
"In the first year of being a mom, I realized there were muscles in my face that had never been used before. When looking at my son, I was smiling in a way I never had before. My face was sore all the time," Linney tells PEOPLE in this week's issue.
"Motherhood changes you on a cellular level. It literally infuses the cells of your body, and they behave differently," she says. "Fatigue is different. Joy is different. Fear is different. Anxiety is different. All of your emotions become more potent."
The Ozark star recently nabbed a Golden Globe and Screen Actors Guild nomination for her role on the hit Netflix show opposite Jason Bateman and can next be seen in the film Falling (out now on demand) directed by Viggo Mortensen. In the drama, Mortensen and Linney play siblings whose father has dementia.
"If Viggo calls and says, 'Do you want to be in a movie with me?' you say yes," she says.
Never miss a story — sign up for PEOPLE's free daily newsletter to stay up-to-date on the best of what PEOPLE has to offer, from juicy celebrity news to compelling human interest stories.
But Linney admits balancing work and motherhood isn't easy.
"I want to be with my child all the time. But that's not possible or realistic or particularly good for him either, for that matter," she says. "You just do the best you can."
Linney, who married husband Marc Schauer in 2009 and had her son later in life at the age of 49, says she is so grateful to be a mom.
"I'm so happy that I have a child. He's been such a gift." she says.
For more on Laura Linney, check out this week's issue of PEOPLE, on newsstands Friday.
Source: Read Full Article