Among the serious results of faulty mental habit must be included also the doubting folly (_folie du doute_). The victim of this disorder is so querulously anxious to make no mistake that he is forever returning to see if he has turned out the gas, locked the door, and the like; in extreme cases he finally doubts the actuality of his own sensations, and so far succumbs to chronic indecision as seriously to handicap his efforts. This condition has been aptly termed a "spasm of the attention." The apprehensive and fretful may show, in varying degree, signs of either or all these conditions, according as circumstances may direct their attention. Passing from serious disorders to minor sources of daily discomfort, there are few individuals so mentally gifted that they are impervious to the distress occasioned by variations of temperature and of weather; to the annoyance caused by criticism, neglect, and lack of appreciation on the part of their associates; to active resentment, even anger, upon moderate provocation; to loss of temper when exhausted; to embarrassment in unusual situations; to chronic indecision; to the sleeplessness resulting from mental preoccupation; and above all, to the futile regrets, the querulous doubts, and the undue anxiety included under the term _worry_, designated by a recent author "the disease of the age." Something may be accomplished in the way of lessening all these ills by continuous, properly directed effort on the part of the individual. Every inroad upon one faulty habit strengthens the attack upon all, and each gain means a step toward the acquisition of a mental poise that shall give its possessor comparative immunity from the petty annoyances of daily life. In modern psycho-therapy the _suggestion_, whether on the part of the physician or of the patient, plays a prominent part, and it is in this direction, aside from the advice regarding occupation and relaxation, that my propositions will trend. I shall not include, however, suggestions depending for their efficacy upon self-deceit, such as might spring, for example, from the proposition that if we think there is a fire in the stove it warms us, or that if we break a pane in the bookcase thinking it a window, we inhale with pleasure the resulting change of air. The suggestions are intended to appeal to the reason, rather than to the imagination. The special aim will be to pay attention to the different varieties of worry, and to offer easily understood and commonplace suggestions which any one may practice daily and continuously, at last automatically, without interfering with his routine work or recreation. Indeed the tranquil mind aids, rather than hinders, efficient work, by enabling its possessor to pass from duty to duty without the hindrance of undue solicitude.