Playing the obvious move will get you beat in chess. Or, in this case a thoughtless capture 67...dxBc2 blows the Black win for a draw. Think BEFORE you capture about what will happen AFTER the capture.

Note that Black has "the wrong colored bishop" to force promotion of the a-pawn. (If you are not already aware that a rook's pawn endgame tends to be drawish, please read some of FTB's prior posts advising general instruction books with history, rules, terminology, tips, opening, middlegame, and endgame chapters. That endgame chapter will reward you again, and again, and again in a pinch after a long struggle like the game above. Once you realize the lasting, repeating value of this endgame wisdom, you'll want to read a specific endgame manual or two to learn how to force wins and save draws in all types of endgame scenarios. [The endgame is handled differently than the opening and middlegame.] But start with those general instruction books from the library or used book store first.)

So the intermezzo 67...a3+ offers a deflection sacrifice for a gain of time. If 68.Kxa3?? dxBc2 69.Kb2 Bxe4 and Black's passed d/c-pawn is protected while also preventing White's passed h-pawn from promotion on the opposite wing. With a secure position on the light squares, Black has the leisurely time to bring up the king to force the White king away from the promotion square on c1 by using the opposition of kings. (The passive White king does not dare go anywhere because it must defend c1, but the Black king will eventually arrive and force his adversary to back away from c1. The White king will have no choice but to back away and allow the pawn to promote on c1.)