‘In looking back on an unpleasant or disagreeable experience, the thought inevitably occurs to us: if only we had said or done x instead of y, if only we could do it over.

Many a general has lost his head in the heat of battle and then, looking back, has thought of the one tactic, the one maneuver, that would have changed it all.’

This quotation is from p 21 of the landmark book, The 33 Strategies of War, by Robert Greene.