The Art of War by active 6th century B.C. Sunzi

8. If our expectation of advantage be tempered in this way, we may

succeed in accomplishing the essential part of our schemes. [Tu Mu says: "If we wish to wrest an advantage from the enemy, we must not fix our minds on that alone, but allow for the possibility of the enemy also doing some harm to us, and let this enter as a factor into our calculations."]