Take the Time to Count.

I had a disappointing drawn in the Region VI Championship. In the following position I played (as black) a combination that reduced to a winning endgame.

black to play

30...Nxe4 31.Nxe4 Rxe4 32.Rxe4 Rxe4 33.Qxe4 fxe4 34.Rxf6 Kxf6 35.Bxe4 Bf5 36.Bxf5 Kxf5 my king is placed much better 37.Kg2 Ke4 38.Kf2 Kd3 39.Kf3 to reach this position.

black to play

Here I messed up badly. I was worried about getting my king trapped on the a-file. I was not in time trouble, I had plenty of time. I messed up the visualization of the position after 39...Kc3 40.Ke3 Kxb3 41.Kd3 Kxa4 42.Kc3

black to play

This is a clear win for black with 42...b5. There is no problem even if  black did not have a b-pawn, because white will have to eventually release control of b4 anyway,. but even though I was not sure this was a win, If I had counted the possible other paths, I would have known that they were at best draws, and this was the best position for me, even if I was trapped and it was a draw.

black to move

This diagram is messy, but the different colored arrows mark moves to make a queen. Without interference, White's red path to queen the d-pawn is 8 moves. Black's green path to queen the c-pawn is 8 moves, but it interferes with white's red path halting it after move 3 (White's cannot move Ke6-d7, because it leaves the d-pawn loose. White's path to queen the g-pawn is 9 moves. Black's counter to that path starts with 39...g5, which is answered by 40.h4 g4+ 41.Kf4 and 8 more moves to queen the h-pawn, but black queening the c-pawn has not started, so it is still 8 moves. The red path for Black counters the white h-pawn plan with a 7 move path, but now the white d-pawn path is 7 moves, because the white king has taken one step. So 39...g5 makes it easier for white to queen a pawn, but no easier for Black. My 39...g5 was a horrible blunder that threw away the win. All resolvable with some counting. Tedious and time consuming, but I had the time. Since all paths but 39...Kc3 were draws or worse, that was the right move, even if it ended with my king trapped.

The key is to visualize each path in turn and count it out.

Addendum: there is a better win after ...Kxb3 41.Kd3.

black to move

41...Kb4! and white will have to abandon the c-pawn. (42.h4 Kb3)

Addendum 2:
For those who are screaming at me, that trapping a king in front of his rook pawn does not work unless the pawn is far advance, I know that now.

black to move

1...Ka3 2.Kc3 a4 and black has the opposition and is released

either to b2 to escort the a-pawn to queen, or to b4 to free and escort the c-pawn. The rook pawn alone in this position would be a draw, because white can get to the queening square, or trap black's king.