Author John Green has confessed he cried "almost every day" he was on the set of the film adaptation of his cult-classic novel, The Fault in Our Stars.
The book and movie follow teens Gus and Hazel Grace as they fall in love, while battling cancer. Shailene Woodley and Ansel Elgort play the iconic roles in the film, which was written by Scott Neustadter and Michael H. Weber.
"I cried a lot. I cried almost every day," Green said at a recent New York press conference.
"Plus, there are some sad parts," Green added. "There are a lot of funny parts, too, but even the funny parts made me cry."
Woodley and Elgort previously played brother and sister in the science-fiction blockbuster Divergent.
Co-starring Laura Dern, Willem Dafoe and Sam Trammell, The Fault in Our Stars opens in U.S. theaters Friday.