ALA, "Jack, i swear-" he could not say anymore, because he couldn't bring the words out. The truth hurts.
I found it ironic that Ennis breaks down because Jack lays everything out in the lake scene, but does not breakdown when Jack is dead. I think this is a illusion to the hard truth. No matter how much we wanted to believe it, Ennis would never be able to say 'i love you'. He could not hear the truth, it hit him some place deep, maybe even harder than the death of Jack. Most of you are willing to argue this point, but isn't the message of the movie 'things don't turn out the way you want them too' or 'the truth hurts'?