...a phenomenon typical of (but not limited to) midlife, whereby people, increasingly aware of the finiteness of their time in the world, the limitations placed on them by their choices so far, and the narrowing options remaining to them, start judging their peers’ differing choices with reactions ranging from envy to contempt.
Joe may be verging on a major disorientation here - a legitimate rent in the cloth. This actually appears in textbooks: Client abruptly begins to see the world in some entirely new way he feels certain, had he only seen it earlier, would've directed him down a path of vastly greater happiness - only (and this, of course, is the insane part) he inexplicably senses that way's still open to him; that the past, just this once, doesn't operate the way it usually operates. Which is to say, irrevocably.
But, as Tim Kreider says:
One of the hardest things to look at in this life is the lives we didn’t lead, the path not taken, potential left unfulfilled. In stories, those who look back - Lot’s wife, Orpheus and Eurydice - are lost.