The basic aim of a pawn sacrifice is to seize the initiative - the overall control of events - and to improve the placing of your pieces. Isaac Lipnitsky, Questions Of Modern Chess Theory
Look around for combinations for yourself at every move; and before playing any move, visualise the whole position with that move made, and look around for combinations for your opponent. Cecil Purdy, The Search For Chess Perfection
Chess is very much a team game. The pieces rely heavily on each other's help and cooperation, so if one does not pull its weight it lets the whole side down. Michael Stean, Simple Chess
The Stonewall (for White) is dubious where Black has developed or can develop his queen's bishop on the kingside. Cecil Purdy, CJS Purdy's Fine Art Of Annotation And Other Thoughts - Volume One
An extra pawn in a rook ending, with pawns on only one side of the board, should usually not be quite enough to win. However, it can still be quite a fight to draw. Jon Speelman, Endgame Preparation