Postscript

Too tired and contented to write more, but the only truly bad five minutes of the day involved riding over this! I was on the verge of hyperventilating and kept on muttering to myself, "I hate bridges! I hate bridges!" But it is a much shorter one than the GWB, fortunately, though the steepness makes it worse in other respects. The strength of my physical reaction even to this much more manageable bridge (you're not riding right next to the edge, there's a shoulder on the road inside of a raised sidewalk) tells me that I shouldn't plan any time soon to ride even in the "good" direction over the GW - it is time-consuming, but I will just have to take the bus back from Lamont as well as to Lamont in the first place.
Photo borrowed from here.

(Editorial disclaimer: I am 98% sure that this is the bridge I rode over, but due to limitations concerning images of places, I can't swear to it! The only other glitch today was that somehow I managed to miss the first aid station completely, which meant I rode from mile 25 to 55 with no fluids - in retrospect, I should have just stopped at a convenience store, but usual anxieties re: getting lost, getting left behind, etc. warred with sensible knowledge that I should make my own arrangements. Of course I also thought it might be that I was about to come up on the real aid station! Still not sure how I missed it, but it is very much the sort of thing that happens to me - key cluster of stuff re: not really recognizing places, not having good intuitive feel for routes, etc.)