Well, the opponent is only rated 1500 here, and I think being able to resist ...e2 is actually a rather advanced thing. The intuitive thought people might have is that ...e2 "stretches" the king by forcing it all the way to e2. Instead black should play 68...Ka6, and of course white is forced to go after the e pawn anyway, at least at some point, as if white moves too far to the left the e pawn will just queen; thus, black has no reason to spend time on ...e2; it is better spent improving his king with ...Ka6. After 69 Kxe3 Kxa5 70 Kd3, black plays 70...Kb4, getting the king in front.
The difference between the two lines is that with 68...e2, white gets his king to e2, but black has not made progress with his own king; 68...Ka6 immediately makes progress with his king, and yet white is still obligated to take on e3. In fact, the king is just as badly placed on e3 as it is on e2 here, as it is just as far away from d3, whether on e3 or e2. So 68...Ka6 gets the king in faster, making a big difference.
I think the above is rather subtle stuff, and I didn't really appreciate those things sufficiently until I was at least a class A player. Perhaps it varies depending on the person.
Please give advice on how to either better my game or how I could've played this game better.