Rose : The hardest part of being so poor, was being so rich. But every time I thought of selling it, I thought of Cal. And somehow I always got by without his help.
It's from the original version of the scene at the stern of the Keldysh, where Rose chucks the big blue rock into the ocean. Originally Bodine, Lizzy and Lovett are present and get a huge shock to discover Rose has the necklace with her. Cameron changed it to Rose on her own, keeping the focus on the Jack'n'Rose story rather than bringing in Lovett's epiphany at that point.
Here you go, from Titanic, James Cameron's Illustrated Screenplay, annotated by Randall Frakes, p151: