Jack makes it clear that he doesn't like being separated from Ennis so much:
" ... Count the damn few times we been together in twenty years. Measure the fuckin short leash you keep me on, then ask me about Mexico and then tell me you'll kill me for needin it and not hardly never gettin it. You got no fuckin idea how bad it gets. I'm not you. I can't make it on a couple a high-altitude fucks once or twice a year. You're too much for me, Ennis, you son of a whoreson bitch. I wish I knew how to quit you."