The film, which is releasing on February 13, is based on the erotic romance novel by British author E L James, reported People magazine.
"I'm literally going out of my mind. I have seen this film over a thousand times and... The nuances within - the tiniest shift, look, blink of an eye - can make all the difference and flip it into the wrong territory. It's like walking a knife edge," she said.
Taylor-Johnson, 47, said she has been breathless ever since she signed on for the project.
