I believe that Ennis was hit with love for Jack like a freight train and it startled him. Their second love scene was so sweet and tender. It sealed the eternal bond between them. Even later in the film, Ennis stated that "there's no reins on this." His love for Jack was a powerful force. And that is one of the things that makes "Brokeback Mountain" so heartwrenching for me. I do not know how Ennis denied himself the "sweet life" he could have had with Jack. And, yes, when Jack mentions that sweet life, it always brings me to tears. And I do not know how Ennis managed to live after Jack was gone. Could Ennis have wondered that Jack could have still been alive had they decided to make a life together? How does any human being "stand it?" :\'( Frankly, were I Ennis, I would have seriously considered taking my own life.