Ben Affleck is opening up about his relationship with Jennifer Lopez while appearing in his wife's documentary, "The Greatest Love Story Never Told." In the documentary, it follows Lopez as she works on not only her new album, "This is Me…Now," but also the high-concept music film "This is Me…Now: A Love Story." At the beginning of the film, Lopez shares that her latest album is based off of a series of love letters that Affleck wrote her. The singer found irony in making a record about "the greatest love story never told" by telling it so publicly.

"Jen was really inspired by this experience, which is how artists do their work," Affleck said. "They get inspired by their personal life, it moves you. I know as a writer and director I certainly do the same things. But things that are private I had always felt are sacred and special in part because they’re private. So, this was something of an adjustment for me."

At a screening for the documentary, Lopez revealed that Affleck was reluctant to participate in the film. "The other scary part was that I was bringing into it my husband, who was kind of the reluctant participant, silent participant and all," she told the audience. "I just said to him during one of the parts of the movie, I was like, 'Is this weird?' He's like, 'Yes.' I said, 'You're crazy.' I told him he was crazy, not me. But I know that I'm a crazy one. I get that part."  Despite being reluctant, Affleck was the one who encouraged Lopez to do the documentary. "It wasn't my idea to photograph every single moment of doing this," she said. "To be honest, when we started making the film, it just kind of got more and more bizarre, and my husband, who had a front seat to the whole thing really, was the one who was like, 'We should be capturing this,' and he brought on this amazing team and that's kind of how it happened." Although he supports Lopez's artistry with the documentary, he still had a hard time with it all. "It’s the first time she’s done something as an artistic form of expression that was purely for the sake of what she had to express. It was about bringing out the things she felt inside just wanted to say," Affleck said. "And I don’t really love being in the making of documentary about my personal life, which is why I’m so relieved that it’s not really — it seems like I might be in this, but not really. I was worrying for no reason. The movie wasn’t about me. It was about the ability to love yourself. And that love story is a lot f---ing harder to find than prince charming."