There are many reasons for being in a bad mood. Body temperature, heartbeat, blood pressure and endocrine are all affected by biological clock. When the biological clock is disordered, there will be psychological and physical discomfort, which will lead to depression and sadness. In addition, climate change is also closely related to mood. People are more likely to feel depressed on rainy days, especially on cloudy days, which will make people feel irritable and even affect their judgment.