Next time you see a position that is supposed to be winning: capture the position, transfer it to your favorite chess program, set the program at a higher rating than your own and play the winning position to see how to conclude the game. Then go back and repeat the exercise at an increased rating until you can win against it at full strength.
The ending below is from my previous post Blogger vs Blogger, OTB. Time remaining on the clock was less than 2 minutes and at that point I was playing for a draw and played gxf5+. gxh5 was the winning move.
For the readers who wish to try this exercise, the FEN is:
8/8/3k2p1/p2PbP1P/1p2K3/1B6/8/8 b - -
Having the passed pawn on the outside (i.e. h-file) makes the difference.