In a hard-fought game my student played that ended in a draw, when we were looking at it, I observed that his opponent missed a win at one single critical moment. This was a result of an accumulation of positionally questionable decisions that, although in themselves still led to defensible positions, led to a single blunder that could have been punished.
Allowing an outside passed Pawn
The first unnecessary concession was made in the late middlegame when Black captured a piece on a5 allowing a recapture with a Pawn bxa5 resulting in White getting an outside passed Pawn. Granted, this being a Rook Pawn made it not as useful, but still created unnecessary danger.
King out of play
The second unnecessary concession was moving the King from g8 to h7, out of the main action. It was best to moving the King toward the center and toward the Queenside, with the goals of safeguarding the Pawn chain from c6 as well as, more critically, aiming toward White’s a-Pawn, either to capture it or at least prevent it from Queening. Granted, Black had a plan to get the King to f4, but it is slow. In fact, it ended up working in the game, but only because White did not act more quickly and decisively to try to Queen the a-Pawn.
Creating another outside Pawn for the opponent
The final concession, which in this case was a big blunder, was to accept White’s sneaky offer of a Queen trade, resulting in transforming White’s c-Pawn into an “outside” b-Pawn that could have been used as a Pawn break to lead the way for White’s King to invade the Queen side and successfully Queen the a-Pawn. A calculation shows that Black’s attempt to also Queen a passed Pawn is too late, because White’s active King can get to Black’s King side Pawns in time to ensure that after White gives up the Rook in turn, the resulting King and Pawn ending is an easy win because Black’s King ends up out of play and White can just push a passed Pawn to victory.
The main lessons to learn are that even in a drawable position, it is wise to keep the draw simple by not giving a passed Pawn to the opponent, not giving a Pawn break to the opponent, and keeping one’s King ready to prevent Queening of a passed Pawn if it does exist.