Even the most proven Hollywood producers have to face fear of failure — plus 500-page first drafts — as they shepherd their movies towards finish line.

Eric Fellner, speaking at Saturday’s Producers Guild of America awards nominees breakfast, admitted that production on “Les Miserables” started on a terrified note.

“Everyone was petrified since none of the actors had sung before on screen so we were thinking we’re going to blow $60 million and no one was going to come,” he recalled.

Instead, “Les Miserables” has topped $300 million in worldwide box office with Fellner noting that the 10 PGA nominees for the Daryl F. Zanuck trophy may eventually hit $4 billion in global gross. The leaders are “Skyfall” with $1.04 billion and Ang Lee’s “Life of Pi” with $500 million.

“I think it’s a great time for audiences,” Fellner added.

“Lincoln” producer Kathleen Kennedy allowed that one of the early challenges she and Steven Spielberg faced was whittling down Tony Kushner’s initial 500 script pages along with focusing on the legislative debate over the 13th Amendment — which constituted only a small part of Doris Kearns Goodwin’s “Team of Rivals,” the source material for the script.

“It was a laborious process,” Kennedy admitted.

“Django Unchained” producer Stacey Sher noted Christoph Waltz had dislocated his pelvis after falling off a horse on the first day of shooting and that Jamie Foxx dislocated several discs later in the 130-day shoot.

“Skyfall” producer Michael Wilson asserted that it’s a producer’s role to reduce the fear factor on sets. “Our job is to insulate the artists,” prompting Lee to quip, “Can I work with you?”

And “Beasts of the Southern Wild” producer Josh Penn pointed out that he and fellow producers Dan Janvey and Michael Gottwald were beset by uncertainty during shooting three years ago.

“None of us had ever made a film before,” he mused. “And we had to find a 6-year-old to carry the movie.”

The event, sponsored by Variety, took place at the Landmark Theater in West Los Angeles, half a day before the PGA’s award of its Darryl F. Zanuck award for top feature. Ben Affleck (“Argo”) provided star power and asserted that the weight of his producing duties were eased considerably by Chris Terrio’s script and by being able to cast exactly who he had sought — such as Alan Arkin for the role of a veteran big-shot Hollywood producer.

“Alan Arkin is the only guy who could have played that part aside from Jerry Weintraub,” he said.

In response to questions by moderator Gary Luchessi, several producers underlined the import of keeping the set undisturbed during production. “I like a quiet set because it allows actors to take risks,” Affleck said.

And Lee, Affleck and Kathryn Bigelow of “Zero Dark Thirty” endosed handling the double role of director and producer. “It’s a tremendous advantage to be both,” Bigelow said.

Lee said producers have to act as adults while directors can act like children. “The director’s side always wins.”

Affleck also noted that his background as an actor gives him an understanding of the frustrations that thespians experience while preventing him from being bowled over when demands become excessive. The panel ended with Affleck recalling that he had asked his brother Casey about acting in a new project.

“He told me, ‘First day — no fruit plate,'” Affleck said, eliciting major laughs from the audience.