Citing numerous unidentified friends of the couple, the New York Post said the couple felt "with all the media pressure and attention, they would be getting married for the wrong reasons."
"It took a lot of strength for those two to call it off. It just turned into a circus. Granted, it was a circus they created. And they know it," one pal said.
The couple tried Wednesday night to show the world they're still a strong couple, going out to dinner with Lopez's friends in Beverly Hills.
The dinner was originally planned as a get-together for Lopez and her three bridesmaids -- producer Elaine Goldsmith-Thomas, her former publicist Karynne Tencer and Shawn Barton.
"Ben was told to go by his publicist and agent Patrick Whitesell," said Affleck's friend. "They went to dispel myths of them not being together. It was a purposeful and public move, but very hard."