The following game was included in Attacking Strategies for Club Players by GM Michael Prusikin, which I'm currently working through during lunch hours at work (when I can take them, that is.) While calculation obviously played a large part in this tactical masterpiece, the final winning idea by Black (GM Eduard Gufeld) is something that I certainly never would even have begun to calculate when trying to generate candidate moves. This highlighted the insight that calculation is not enough - one has to first have the necessary ideas in mind, then recognize that the position in front of you may allow them to work. (The related training quote of the day #47 is relevant as well.)
In this case the sequence beginning on move 24, which uses the concepts of clearance and deflection sacrifices, is particularly striking. The necessary move of simply hanging your bishop (move 25) is highly unlikely to occur to anyone employing a "brute force" type of thought process. Understanding that this move will both clear the 8th rank for the queen and divert the protection of the c4 square are both necessary ideas. Clearance sacrifices in particular I think are a sign of mastery, and I expect will be a separate topic in the future.
