Alicia Vikander said she was "totally able to relate" to the fears of her character in The Danish Girl, whose husband becomes the world's first sex reassignment patient.
The Swedish actress stars as real-life artist Gerda Wegener who supports her husband Einar - played by Eddie Redmayne - as he comes to accept he is transgender and eventually undergoes the groundbreaking surgery that allows him to live as Lili Elbe.
She said she was able to empathise with "the fear of thinking that a change will mean you lose the person that you love".
"It feels like I was totally able to relate to this marriage and relationship in a way of going on a big journey," she said.
"When a big change is happening, they kind of have to find new feet and new ground and how this consolation between them is going to work and it's the fear of thinking that a change will mean you lose the person that you love. But what's extraordinary is the fundamental love and support between them in this film."
The 27-year-old said that it became a "big deal" to her to play Gerda as she researched the life of the Danish painter.
"This film has been so inspirational but also educational as well: just going back to playing characters that exist in real life and trying to find as much information as you can about these two women, about Gerda, to find out about her art, about a woman who was not only an artist but a working woman in the 1920s.
"I was extremely honoured because I was so impressed by her as a person.
"To try and portray a woman like her was a big deal. She is able to support a person she loves to the extent where she can sacrifice and be extremely unselfish. I find her extraordinary," she said.
Critics have praised both her and Redmayne's performances in the film, but while she said Oscar buzz was "wonderful", she felt "immune to it all".
The actress, who spent three years surviving on just £200 a month while struggling to make a name for herself, released eight films this year, including Testament Of Youth and Ex Machina.
Vikander - who is dating Michael Fassbender - said her schedule, including just a two-week break during back-to-back projects and never knowing when the next role might come up, had been "tough" on her personal life.
"You're on your toes all the time and I think that's very exciting. The only thing that is quite tough sometimes is the personal aspect of family and friends. People actually ask you, 'So what are you doing in three months?' I don't know, but I don't know if I can make any plans," she explained.
With her roster of films to promote, Vikander admitted she had never done so many press interviews in her life, including 102 in just two days while pushing Guy Ritchie's film Man From U.N.C.L.E.
But she claimed the worry of finding herself jobless is unrelenting.
"It's always there, it's the scary thing I think most actors carry that with them. You never know what's around the corner, even if you're lucky to know what's next, that's still just a few months ahead of what you're doing at the moment," she said.
She stars next alongside Fassbender in The Light Between Oceans and in the as-yet-untitled new Bourne film with Matt Damon.
:: The Danish Girl is out in cinemas on Friday.