Novelist and screenwriter Larry McMurtry, 69, says the core theme of Brokeback Mountain is that “life is not for sissies,” which of course means that he thinks Heath Ledger‘s Ennis del Mar character is one. He’s right, of course. The immense sadness that BBM leaves you with at the finale is all about this middle-aged cowboy’s realization that he’s blown it by failing to make something out of his deep-river feelings for Jake Gyllenhaal’s Jack Twist. A Pulitzer Prize winner and BBM co-screenwriter (along with Diana Ossana), McMurtry is an Oscar nominee for Best Adapted Screenplay. He let go with his del Mar diss during a taping of “CBS News Sunday Morning” that will air this coming Sunday (2.19). “You need strength…love is not easy,” he said. “It’s not easy if you find (it), it’s not easy if you don’t find it. It’s not easy if you find it but it doesn’t work out. [Our film] merely says the strong survive, but not everybody is strong.”