凡病朝慧者，以朝则人气始生，卫气始行，故慧也。昼安者，以日中则人气长，长则胜邪，故安也。夕
加者，以夕则人气始衰，邪气始生，故加也。夜甚者，以夜半人气入脏，邪气独居于身，故甚也。此百病消长
，邪正进退之常也。凡病来潮，发作之时，精神为贵。病至精神不衰，则为邪气不能胜正，正气实也。病至
精神困弱，则为正气不能胜邪，正气虚也。
凡病昼则增剧烦热，而夜安静者，是阳自旺于阳分，气病而血不病也。凡病夜则增剧寒厥，而昼安静者，
是阴自旺于阴分，血病而气不病也。凡病昼则增剧寒厥，而夜安静者，是阴上乘于阳分之病也。凡病夜则增
剧烦热，而昼安静者，是阳下陷于阴分之病也。凡病昼夜俱寒厥者，是重阴无阳之病也。凡病昼夜俱烦热者，
是重阳无阴之病也。凡病昼则寒厥，夜则烦热，名曰阴阳交错者，饮食不入，其人之死，终难却也。
凡食多气盛，此其常也。若食多气少，非胃病火化，即新愈之后，贪食而谷气未足也。凡食少气少，此
其常也。若食少气多，则必是胃病不食，肺病气逆，两经之愆也。喜冷者，中必有热；喜热者，中必有寒；虚
热则饮冷少，实热则饮冷多，虚寒则饮热少，实寒则饮热多，是寒热虚实，辨在多少之间也。如
伤食不思食。若杂证思食，为有胃气则生，绝食为无胃气则死。
凡是早晨病情缓解的，是因为清晨人体正气开始生发，卫气开始运行，所以精神清爽。白天病情平稳的，是因为中午时分人体正气旺盛，正气旺盛就能克制邪气，所以病情安稳。傍晚加重的，是因为傍晚时人体正气开始衰退，邪气开始亢盛，所以病情加重。夜间严重的，是因为半夜时人体正气内入于脏腑，邪气独自留滞于体表，所以病情严重。这是各种疾病消长、邪正进退的一般规律。
大凡疾病发作如潮水般有定时，此时观察患者的精神状态最为关键。发病时如果精神不衰，说明邪气不能战胜正气，属于正气充实；发病时如果精神困倦虚弱，说明正气不能战胜邪气，属于正气虚弱。
凡是白天病情加重且伴有烦热，而夜间安静的，是阳气在阳分自然偏旺，属于气分有病而血分无病。凡是夜间病情加重且伴有寒厥，而白天安静的，是阴气在阴分自然偏旺，属于血分有病而气分无病。凡是白天病情加重且伴有寒厥，而夜间安静的，是阴气上乘于阳分的病变。凡是夜间病情加重且伴有烦热，而白天安静的，是阳气下陷于阴分的病变。凡是昼夜都出现寒厥的，是重阴无阳的病变。凡是昼夜都出现烦热的，是重阳无阴的病变。凡是白天寒厥、夜间烦热的，称为阴阳交错证，如果此时饮食不进，病人的死亡结局终究难以避免。
凡是进食多而气息壮盛，这是正常现象。如果进食多而气息微弱，不是胃火炽盛（消谷善饥），就是大病初愈后贪吃，但谷气尚未恢复充足。凡是进食少而气息微弱，这是正常现象。如果进食少而气息反而粗多，那一定是胃病导致不能进食，或是肺病导致气机上逆，这是胃和肺两经的过失。喜欢冷饮的人，体内必有热邪；喜欢热饮的人，体内必有寒邪；虚热证饮水冷者较少，实热证饮水冷者较多；虚寒证饮水热者较少，实寒证饮水热者较多，寒热虚实可以通过饮水量的多少来辨别。如果是伤食导致的不思饮食，与杂病中想要进食的情况不同：杂病中若能思食，说明还有胃气，预后良好则生；若完全绝食，说明没有胃气，预后不良则死。
In cases where symptoms improve in the morning, it is because at dawn, the Zheng Qi (Upright Qi / Healthy Energy) begins to generate and the Wei Qi (Defensive Qi) begins to circulate, hence the clarity of spirit. In cases where symptoms are stable during the day, it is because at noon, the Zheng Qi grows strong; when strong, it overcomes the Xie Qi (Pathogenic Factor), hence the stability. In cases where symptoms worsen in the evening, it is because at dusk, the Zheng Qi begins to decline and the Xie Qi begins to flourish, hence the worsening. In cases where symptoms are severe at night, it is because at midnight, the Zheng Qi enters the Zang-Fu Organs, leaving the Xie Qi to reside alone in the body, hence the severity. This is the general pattern of waxing and waning in all diseases, reflecting the advance and retreat of Xie Qi and Zheng Qi.
Generally, when a disease manifests with tidal regularity, observing the Shen (Spirit/Mental State) is paramount. If the Shen remains unimpaired upon onset, it indicates that Xie Qi cannot overcome Zheng Qi, signifying excess Zheng Qi. If the Shen becomes fatigued and weak upon onset, it indicates that Zheng Qi cannot overcome Xie Qi, signifying deficiency of Zheng Qi.
In cases where symptoms aggravate during the day accompanied by vexatious heat, while remaining quiet at night, this indicates Yang naturally flourishing in the Yang aspect, denoting a disease of Qi but not Blood. In cases where symptoms aggravate at night accompanied by cold extremities (Han Jue), while remaining quiet during the day, this indicates Yin naturally flourishing in the Yin aspect, denoting a disease of Blood but not Qi. In cases where symptoms aggravate during the day with cold extremities, while remaining quiet at night, this is a pathology of Yin surging upward into the Yang aspect. In cases where symptoms aggravate at night with vexatious heat, while remaining quiet during the day, this is a pathology of Yang sinking downward into the Yin aspect. In cases where cold extremities occur both day and night, this is a pathology of Repeated Yin without Yang. In cases where vexatious heat occurs both day and night, this is a pathology of Repeated Yang without Yin. In cases where there are cold extremities by day and vexatious heat by night, termed "Yin-Yang Interlacing," if food intake ceases, death is ultimately inevitable.
Consuming much food with robust Qi is the normal state. If one consumes much food but has weak Qi, it is either due to Stomach Fire transforming (increasing appetite) or, after recovery from illness, greedily eating before Gu Qi (Grain Qi/Nutritional Energy) has sufficiently recovered. Consuming little food with weak Qi is the normal state. If one consumes little food but has excessive Qi (rapid breathing), it must be due to Stomach disease preventing eating, or Lung disease causing Qi rebellion; this is an error involving both meridians. Those who prefer cold drinks must have Heat in the interior; those who prefer hot drinks must have Cold in the interior. In Deficient Heat, consumption of cold drinks is scanty; in Excess Heat, consumption of cold drinks is abundant. In Deficient Cold, consumption of hot drinks is scanty; in Excess Cold, consumption of hot drinks is abundant. Thus, Cold/Heat and Deficiency/Excess can be distinguished by the quantity of intake. For example, loss of appetite due to Food Retention differs from craving food in miscellaneous diseases: craving food in miscellaneous diseases indicates the presence of Stomach Qi, leading to survival; total absence of desire to eat indicates the absence of Stomach Qi, leading to death.