We must contemplate some extremely unpleasant possibilities, just because we want to avoid them and achieve something better. Nobody, however, likes to think about anything unpleasant, even to avoid it. And so the crucial problem of thermonuclear war is frequently dispatched with the label 'War is unthinkable' -- which, translated freely, means we don't want to think about it.
Almost everyone seems concerned with the need to relax tension. However, relaxation of tension, which everyone thinks is good, is not easily distinguished from relaxing ones guard, which almost everyone thinks is bad. Relaxation, like Miltown, is not an end in itself. Not all danger comes from tension. The reverse relation, to be tense where there is danger, is only rational.