Andra Day is the darling of awards season as a first-time Oscar nominee for her revelatory performance as the titular musical icon in The United States Vs. Billie Holiday. But as the Grammy-nominated singer tells PEOPLE, she wasn't fully confident in her performance. In fact, Day presumed she "was retired" from acting altogether after completing the Lee Daniels-directed film.
"I truly was definitely out of my depth the entire time," Day, 36, recalls of making the film ahead of Sunday's 93rd Oscars ceremony. "I had to just trust what my cast was saying or what Lee was saying. I would have the thought, in my mind, that maybe they're just settling because they realized they can't get any better from me. Or that's the best they're going to get, and I'm already here. So there was always that underlying thought that they're just accommodating me right now."
Paramount Pictures Andra Day in The United States vs. Billie Holiday
The Hulu film recounts the way Holiday played a pivotal role in the start of the Civil Rights movement with one of her impactful songs about lynching. For Day, playing the "Strange Fruit" singer was a full circle moment, having taken her stage name as a young performer from Holiday's nickname, "Lady Day."
"Some people might say fate, some people might say universe. But for me personally, it's my belief in God," Day, who recently participated in an Amazon Music livestream panel with her creative director Myriam Santos, says of how she came to the role.
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.
The experience of portraying Holiday, who wrestled with drug addictions until her death at the age of 44 in 1959, took a toll on Day in her first major film role.
"If you could envision or feel somehow in your body, what it feels like to be operating purely on adrenaline for three and a half, four months straight. That's really what it was on set for me," Day says. "It was literally like three days without sleeping. But adrenaline is some s---."
As Day previously revealed, she lost 39 pounds to prepare for the part, telling PEOPLE Every Day podcast host Janine Rubenstein that she "couldn't look too muscular" and had to look thin as a result of "starvation and drugs."
"I started to smoke cigarettes. I picked up the habit and started drinking a lot of gin a lot," the actress — who doesn't recommend that to others for health concerns — said.
Despite the intensity of the experience, Day tells PEOPLE she'd likely act again if the part is right.
"The reality is, if I'm agreeing to do roles, it has to grab me, the way Billie grabbed me," she says. "And I don't mean like being intrigued, meaning my spirit has to be sort of be called out to it. Because that's really what Billie was."
The United States Vs. Billie Holiday is streaming on Hulu.
Listen below to the episode of our daily podcast PEOPLE Every Day for more on the 2021 Oscars.
The 93rd Academy Awards will air live on Sunday, April 25 starting at 8 p.m. ET/5 p.m. PT on ABC.