I believe I was winning until move 27. His 14.h19 was brilliant, but I found a way to deal with it, with my j18, f16 (15.j18, 23.f16) combo reply to create a gauntlet for any ladder chase coming down from my p14 peg. At move 19, György tempted me to blunder: the more obvious 19.d9 would have been disastrous for me (19.d9 20.e4, and then 21.h9 22.j6 23.g5 24.g7 25.c7 26.d6, for example). At move 27, I basically flipped a coin in my mind between |27.L14 and 27.n13, which I erroneously thought were effectively equivalent. |27.n13 was my original plan (before György's 16.i8 ... 18.e8 diversion) so I went with it. Unfortunately, it has a fatal flaw that |27.L14 does not have, and that it did not have before the 16.i8 ... 18.e8 diversion. And that's how I snatched defeat from the jaws of victory.

Why not 21.d9?

It took me a while to reconstruct the reason, though at the time of the game it seemed fairly obvious. Hmm, now it seems obvious again. Anyway, I think it's because:

|21.d9 22.g7 23.e7 24.e4 25.e3 26.f2 27.d5 28.d3 29.f4 30.h3, or
25.d5 26.c3 27.f4 28.g3.

and I might not have seen this at the time, but also
if 25.g6 then 26.g3 27.j4 28.h5.