"Imagination is a powerful deceiver. Much of what we think about warfare in general and future conflict in particular comes from the imagination. Sometimes, the images that emerge from our minds can be accurate and useful, but sometimes they are totally false. One such image that serves to warp our understanding of war is the fiction that our enemies are ready for battle.Military units are perpetually unready to fight. Unreadiness is the natural condition of all forces, both friendly and enemy. Combatants in war are almost invariably oriented in the wrong direction, estimating the wrong threat, unsupplied, unrested, in bad terrain, ill informed, physically unfit, morally unprepared or technically dislocated. Our mind's eye, conditioned as it is by our innate fears, fails to perceive this extreme condition of unreadiness, but it is there nonetheless.Forces in war remain unready for combat for virtually the entire duration of the conflict, attaining a degree of readiness for only the briefest of moments before lapsing into unreadiness again. Even when they are ready, they are prepared only for a narrow band of threats. Any threat that emerges outside of that band will again cause unreadiness.If it seems that I have overemphasized this remarkable and lamentable condition of military forces, it is because official doctrine and training within the armed forces does just the opposite: They perpetuate the myth that our enemies are always ready to fight. This is a dangerous and totally inaccurate view of the battlefield, and it is one reason why American tactical doctrine has never learned to capitalize on the principle of surprise. There can be no surprise apart from the condition of unreadiness."
On the one hand, overestimating the opposing force leads to a waste of opportunities, on the other it leads to ill-advised dissatisfaction with one's own security and thus an overemphasis on defensive efforts.
There's a similar problem with survivability. I stress it a lot, but perfect is the enemy of good enough. Every tatcic tends to be accused of being risky in one regard or another, which is largely irrelevant if it's still the best option. One has to weigh the risks with the utility attained, and then compare with alternative approaches - particularly the status quo.
Any improvement is worth it, including improvements over improvements. The existence of a downside in a proposal for improvement is no reason to omit it.
So even someone who's very much concerned about survivability does well to accept that war (and life in general) doesn't know absolute safety.
Another similar problem exists regarding moral robustness. Exercises used to (I have hardly any knowledge of more recent ones) go on until the casualty rates were ludicrous. 80% reduced parties would fight on. In reality, they'd have broken and fled after taking 10-40% casualties (according to miltiary history documents). This wrong depiction of the opposing forces leads to an overemphasis on destruction in pitched battle, and an underemphasis on (preparations for) pursuit.
Historically, many if not most battles saw more men slain during pursuit than before the army broke. An example was Napoleon's 1806 campaign against Prussia, in which the double battle of Jena-Auerstedt actually saw much less Prussian losses than the long, determined and merciless pursuit to Eastern Prussia. A general who would have focused on winning the battle alone would have had to fight twice as many or even more battles to achieve the same end.