Lancôme's new "I'm Fine" campaign opens with a stark number: 80 percent of women say "I'm fine" most of the time, according to a large study the brand conducted. The campaign, developed with the Anxiety and Depression Association of America (ADAA) and the nonprofit HealthyWomen, aims to push women to check in with themselves more honestly.

Vanessa Kirby, a new face of the brand, stars alongside Christy Turlington and Zoë Saldaña, each sharing personal testimonial videos for the cause. Kirby, who played Princess Margaret in Netflix's The Crown, spoke to ELLE about the mental health shift that changed her relationship with herself.

What changed Kirby's inner voice?

"A big shift in my life happened when I gained awareness that my inner voice is not always me, it's thoughts," Kirby said. "Thoughts can be based on conditioning, childhood, or thousands of small internalized belief systems."

She describes that awareness as a journey of dismantling thoughts that don't match what she actually feels and believes. A metaphor helped: "Imagine a sky and the thoughts are the clouds, and they pass by. The sky is the constant."

Kirby calls the goal a "loving detachment" — observing thoughts without judging them. "Instead, you can go, I'm just going to observe with love and see what it's doing right now," she said.

She now measures her mental health by how she speaks to herself. "I personally gauge mental health in how I speak to myself," she told ELLE, pointing to the hours spent alone with her own thoughts — in the middle of the night, before bed, first thing in the morning.

Why does "I'm Fine" resonate with her?

Kirby connects the campaign's title to the Hoffman Process retreat, where saying "I'm fine" in the morning is not allowed. "'It's fine' is just so nondescript," she said.

In her experience — and in her British family and circle of friends — the phrase serves others, not the speaker. "Saying 'I'm fine' is a way to make other people feel comfortable rather than saying, 'You know what, I'm actually having a shitty day,'" she said.

Hiding a bad day, she argued, puts people at war with their own thoughts. The brand's 80 percent statistic is exactly why she signed on. "I'm glad that there's a campaign that is trying to reach people," she said.

The partnership also carries personal weight. "My mum has a long history with the brand, and she's used it for a really long time," Kirby said of Lancôme.

How does acting shape her view of mental health?

Kirby frames acting as "the art of literally thinking someone's thoughts." She credits playing Princess Margaret with letting her imagine how a psyche forms when an older sister is chosen as the more important one — a life spent oscillating between grandiosity and feeling "totally not special at all."

"It's been such a gift of my life to be able to just imagine different women's lives," she said.

One character left a lasting mark: Tallie in Mona Fastvold's film The World to Come. Despite living in a culture that suppressed women's freedom, "she had such a positive, optimistic, expansive view on life," Kirby said. "She always saw beyond the limitations of what was in front of her."

What routines does she keep?

Kirby maintains a regular meditation practice, built over many years through guided meditations and a transcendental meditation course she "absolutely loved." She is candid about inconsistency: some weeks she meditates often, others not at all.

Her benchmark is flexible. "Sometimes, just doing a minute of deep, deep breathing and lying down for a second is just as valuable as doing two sessions of transcendental meditation a day," she said.

Motherhood, she added, has been "a very beautiful, humbling, expansive experience." Her daughter's needs come first, and self-care becomes something to find where she can.

With testimonial videos from Kirby, Turlington and Saldaña rolling out, Lancôme and its two nonprofit partners are betting that naming the "I'm fine" reflex — and its 80 percent prevalence — will give women permission to answer the question differently.