The character of sleep depends largely on the mental attitude on going to bed. One should get into the habit of absolutely dropping work and cares at bed-time. If then one suggests to himself the pleasantest thought which memory or imagination can conjure up, his sleep is likely to be far more peaceful and restful than if he takes his worries to bed, to keep him awake until sleep comes in spite of them, and to continue to plague him in his dreams. If one is worried, it is a good plan to read something diverting, but not exciting, just before retiring. Section II--Serenity and Poise As we have seen, not only the body but the mind needs its due activity and rest. As to the mind, the important question is the quality of the activity rather than the quantity. If we are to be really healthy, our mental attitude must be healthy. A healthy mental attitude implies many elements, but they are all roughly summed up in the word "serenity." Probably no other one hygienic requirement is of greater importance than this. Moreover, the attitude of "healthymindedness" should be striven for not only in order to produce health, but as an end in itself, for which, in fact, even health itself is properly sought. In short the health of the body and the health of the mind act and react on each other. [Sidenote: Influence of the Health on the Character] We may generally keep serene through following the other measures already described. Discontent is undoubtedly very often the consequence of wrong conditions in the body, and though melancholy, worry, peevishness, fear generally appear as arising from outward conditions, there are usually real physical sources, existing within the body itself. These are at times most difficult of recognition. A person who is physically ill is likely to be ill-satisfied with everything, without suspecting the fundamental cause of the discontent. When the apparent "cause" is removed, the discontent remains none the less, and fastens itself on the next thing that comes along. [Sidenote: The "Cause"] Although some little event such as the mistake of a tradesman or a cross word of a friend may seemingly "cause" a disagreeable reaction in a man if he is ill (whether he knows he is or not), the same "cause" does not necessarily produce that same reaction at all times. When he is in a healthy mood, the "cause" may be entirely inadequate to bring about the same result. [Sidenote: Approach of Menstrual Period] The near approach to the menstrual period in women is often accompanied by mental depression and physical fatigue which it is almost impossible for the sufferer to recognize at the time as caused by anything but "real" or outside misfortunes. [Sidenote: Hidden Causes]