一朝一夕 — “In a very short period of time”

The idiom "一朝一夕" (yī zhāo yī xī) originates from a story during the Warring States period. The famous philosopher Yang Zhu, known for his vast knowledge, was highly respected. One day, he visited his friend Ji Liang, who was feeling unwell and resting in bed.

Ji Liang's son, upon seeing Yang Zhu, cried and pleaded, "Uncle Yang, my father's illness appears quite severe. Could you please help me find a doctor to treat him?" Yang Zhu examined Ji Liang and comforted his son, saying, "Don't worry, my nephew. In my opinion, your father's illness is not serious. With proper care, he will recover quickly."

However, Ji Liang's son did not believe him and promptly invited three doctors. The first doctor, after diagnosing Ji Liang, declared, "The cause of your illness is unregulated exposure to hot and cold, an imbalance of strength and weakness, disharmony of yin and yang, and irregular eating habits. Just a few doses of medicine will cure it." Ji Liang shook his head and said, "You are just an ordinary doctor. Please leave!"

The second doctor took Ji Liang's pulse and explained, "Your illness is due to congenital deficiencies, not something that developed in a day or two. It would be very difficult to cure your illness with medicine." Ji Liang approved, saying, "You are a good doctor."

The third doctor merely observed Ji Liang's complexion and stated, "Your illness is caused by mental depression. Therefore, there's no need for medicine; just cultivate your mind and temperament, and you will get better." Ji Liang highly approved, exclaiming, "You truly are a divine doctor!"

Indeed, Ji Liang's illness was caused by mental depression. After adjusting his mental state, he recovered completely not long after.