Credit: Horst Diekgerdes

Disney's Cinderella finally comes out tomorrow and we can't get enough of star Lily James. Not only has the actress wowed on the red carpet lately in princess-worthy looks (Elie Saab, Dior, Prada, oh my!), but she has seamlessly taken on one of the most beloved characters of all time—and done it justice. So when we caught up with James for our March issue's fashion feature, we wondered, what was it really like to step into those famous glass slippers?

"As much as we all wanted to be princesses growing up, the reality of actually being one was sometimes terrifying," James told us. "It's hard to live up to that for everyone." To help her transform into Ella, as she is called in the movie, the actress relied on yoga to get fit for the waist-cinching ball gown. "When I put on that dress, my posture changed and it was sort of magical," she says. "But my hair and makeup team were the real fairy godmothers on set!"

Though the costumes, designed by Oscar winner Sandy Powell, were a dream for James, she was also delighted to work with one of her style icons Cate Blanchett. "Cate is remarkable," says James of Blanchett, who plays the stepmother. "She always wears beautiful, clean lines and I really admire her as woman." James's other red-carpet inspirations, include fellow Brits Alexa Chung ("I love that she never looks too done.") and Keira Knightley ("She always looks stunning!").

Even with all the glamour surrounding the film, James says that the fairy tale's positive message is what really drew her to the role. "My favorite part is when Cinderella tells the prince, 'I have no carriage, I have no gown, no parents, this is just me. And the fairy godmother says, 'This is the greatest risk we will ever take—to be truly seen as we are.' Because it's true, isn't it?"

For more on Lily James, pick up InStyle’s March issue, available on newsstands and for digital download now.