Taking on the role of Cheryl Stayed in the 2014 film adaptation of her memoir "Wild: From Lost to Found on the Pacific Crest Trail" was a daunting prospect for the 45-year-old actress, and had a big effect on her mental health.
Speaking to Tracee Ellis Ross for Interview magazine, Reese explained, "I was so scared to do that, Tracee. I had hypnosis, I was so scared. I was having panic attacks for three weeks before I started."
And it wasn't just the "nudity, sexuality, and drug use" that Reese was worried about, but also how much of the film focused on her - and her alone.
"I hadn’t ever been alone in scenes for days and days," she added. "There were probably 25 days of the shoot where I had no other actor opposite me."
"It was just me and a camera and a backpack. I was like, 'Is this going to be so boring?' "
But at the end of the day, Reese realised that the impact the movie would have was more important, "because it spoke to me so deeply about how we as women have to save ourselves."
"There's no mother or father coming to save us. There's no spouse," she continued. "I thought it was radical that at the end of the film, she ends up with no family, no money, no job, no partner, and she's happy."