"We could have had a good life together, but you didn't want it Ennis. " I don't have the script in front of me, so perhaps I erred in my remembrance.
Well Jack doesn't die right away after saying the a.m. line, but the first time I heard it, I knew the film was drawing to a very unhappy ending. I still think THAT line sums up the movie pretty well; lost opportunities, what might have been.
For Jack, it's almost like him saying "Oh, happy dagger, this is thy sheath; there rust and let me die."

Well Jake said his character "died" when he realized he couldn't be with Ennis so that where I got the connection with R and J.