For Jennifer Aniston, filming her upcoming drama "Cake" was no walk in the park. Just recently, the actress revealed that shooting a scene in the movie made her confront one of her biggest fears.

In an appearance at West Hollywood's Harmony Gold Theater for a special screening of "Cake," Aniston shared her scary childhood memory, "I basically have a fear of going under water," the 45-year-old actress revealed, as quoted by Us Weekly. "As a kid I was with my brother and [I] was driving my tricycle around the swimming pool and drove my tricycle into the swimming pool and I didn't let go."

Claire, the actress's character in the film who battles chronic physical pain, had to be submerged in a pool as a form of physical therapy, according to a report by PEOPLE.

"To get the one shot of me going under with the weights, I think we did that 30 times," she said. "It was the hardest day of my life."

Aside from the struggles of having physical pain, PEOPLE noted that "Cake" also explores addiction to pills and alcohol, which Aniston's character is guilty of.

"I unfortunately have watched a lot of very extraordinary people suffer pretty extraordinary circumstances due to [addiction]," the "FRIENDS" alum said. "But what was really eye-opening to me was that [in] the chronic pain community ... these people are just trying to feel normal and feel a flicker of nothing for a second."

As expected, Aniston's hard work in the film paid off. PEOPLE further noted that the actress has received several acting nominations from the Golden Globe, SAG (Screen Actors Guild) Award, and Broadcast Film Critics Associations Award.

Because of all the favorable response to the movie, the actress expressed her utmost appreciation to everyone who believed in their movie project.

"We were a teensy-weensy movie made for four dollars and we poured our hearts into it and everyone worked so hard, so that this is happening on top of that, it's just like a huge giant juicy cherry on top," Aniston said, as quoted by the news outlet.

Dr. George Graf, founder of the Advanced Pain Treatment and Diagnostics Medical Group and one of the attendees of the special screening of "Cake," praised Aniston's performance in the film.

"What Jennifer did in this movie was remarkable, because I see patients like that every day of the week," the doctor said, according to PEOPLE. "It's not easy to take all of that on and do it."

Aside from Aniston, the film also stars Adriana Barraza, Anna Kendrick, Sam Worthington, Felicity Huffman, Mamie Gummer, and William H. Macy. It was directed by Daniel Barnz and written by Patrick Tobin, according to the film's website.