A lead in development is an ephemeral advantage; it cannot grow indefinitely. The proper technique to exploit a superior mobilisation of forces is to transform it into a more lasting sort of advantage. Lluís Comas Fabregó, True Lies In Chess
After every game, try to think of three new things you have learned. You will find this is not always so easy, but it is a very useful exercise nonetheless. Jacob Aagaard, Excelling At Chess
In planning your game, arrange your pieces in such a way that they are of maximum use and cooperate well with one another. Strive for harmony! Vladimir Popov, Chess Lessons
If there is a 'good forcing move' available, it is probably the best move on the board, or, at any rate, the only move likely to be better is another forcing move. Cecil Purdy, The Search For Chess Perfection
For the offer of a pawn (in the opening) there must be one of four reasons: a) secure a tangible advantage in development; b) deflect the enemy queen; c) prevent the enemy from castling, either permanently or for several moves; d) build up a strong attack. Reuben Fine, The Ideas Behind The Chess Openings
When faced with an unfamiliar opening, or even an unfamiliar move in an opening you know, your first reaction should be to take a deep breath and try to understand what your opponent is doing. John Watson, Mastering The Chess Openings - Volume 4