The Hot Potato Game
This seems to happen a fair bit. I and an opponent play just fine through most of the game, then both our games go to pieces towards the end. It's not even like I don't know endgame technique. I near enough memorised each topic in "Silman's Complete Endgame Course". I just seem to struggle in making the correct decisions in the transition from midgame to endgame. Apparently I am not alone in this struggle, as often my opponent mirrors this, as in the following game.
Note: We were not in time trouble even at the end. Time control was 90 minutes sudden death, and we each had used only about half of that by the 35th and final move. I had about five minutes or so less on my clock than he did, so I was aware of being somewhat obliged to be fairly spritely in my rate of play, while still acknowledging that nearly an hour left on the clock is hardly time trouble.