Powerful passed pawn
People always say that the value of pieces depends on the position on the board. One of the most dramatic ways a piece changes it's value is when a pawn becomes a passed pawn and creeps closer to it's new life as a queen, or short of getting the full promotion, a rook, bishop, or knight.
Some famous words have been said about passed pawns:
"A passed pawn is a criminal, who should be kept under lock and key." -- Aron Nimzowitsch
"Passed pawns must be pushed!" -- Probably Nimzowitsch again, but I've seen quotes of Tartakower and Dvoretsky saying this as well.
Let's look at these plucky little heroes in action. The first game is one that I lost, partly because I mis-evaluated the position and wanted to win. I wasn't satisfied trying to draw and weakened my position in search of an advantage.
In the second game, My opponent built a strong attack and won my queen. White continues to attack with rook and queen, but the creation of a passed pawn gave me the chance to create complications. When the attacker failed to deal with the criminal, I was actually able to create winning chances and finally bring home a victory.