6 ideas
Struggle can be theorized by imagining an ideal combatant, which Lasker calls the 'Macheide', who never wastes a move, a resource, or an effort. The theory does not describe how real people fight. It describes what perfect economy would do, so any real player's choices can be measured by how far they fall from that standard.
In any contest, the side that achieves its aim with the least expenditure of force prevails, because every surplus effort is capacity taken away from somewhere else it will be needed. Brilliance that spends more than the position requires is a strategic loss, not a gain.
A move's quality is relative to the specific opponent who must answer it, because that person has limited information, habits, and discomforts. The practical question is less 'what is objectively best?' than 'what will this opponent, under uncertainty, handle worst?' Choosing positions the opponent dislikes can outperform choosing positions that are theoretically superior.
Most real positions are too complex to calculate to the end, so decisions must rest on evaluating general features such as structure, mobility, and weaknesses rather than on enumerating variations. The skill that matters most is therefore estimation, a trained sense of which features outweigh others, not raw lookahead.
An attack is justified only by an existing advantage in position, and launching one without such an advantage wastes force and invites refutation. Conversely, the side that holds an advantage must attack, because advantages are perishable and dissipate if left unused. The right posture is dictated by the balance of the position, not by temperament.
The worth of a piece or resource is not fixed. It is a working estimate based on the opportunities and mobility it has in the current situation. Standard values are averages that serve as starting points, and good judgment revises them when a resource becomes unusually active or unusually hemmed in.