To Ariel's post about the Shrouded Traveler, my attention was caught by this passage as well. What I think it is, is the subtle uneasiness that Sal feels every time he remembers that he hasn't reached his heaven. I think he is in despair that this "heaven" keeps escaping his grasp and running farther and farther away in the confusing jumble of his life, and that eventually time will run out and he will never get it. Of course I could be completely wrong, but that's what I think.