What eventually happened was that the movie was delayed — not unlike another set of movies that Cameron’s currently working on — finally opening on December 19, 1997 in the U.S., where it held on to the top spot at the box office for a staggering 15 consecutive weeks.
In context, Cameron says he was getting hammered, for racing to meet special-effects deadlines so that Titanic could open in July, as intended.
This account comes from straight from James Cameron himself, who penned this letter to THR’s Stephen Galloway for a book he’s writing on Paramount chief Sherry Lansing — who was instrumental in helping fund Titanic when Cameron was laboring on bringing the movie to the big screen.