Thanks for the questions raised by the host, and I have benefited from everyone's communication.These questions are what we will have to become a qualified trader.
So I briefly summarized everyone's views:

1. "Fear the market and always keep a clear mind; the lesson of loss is more than profit; don't put most of the funds in the exchange" (find a trusted exchange) to ensure your transaction;

2. Greed is a big taboo, and stop loss is a common operation;

3. "A lot of investigation, analysis, and trading strategy should be made before trading, and then invest again";

4. "Ignorance, FOMO, greed and panic are the most important things to avoid in trading". Control your emotions;

5. Check, review and correct your own transactions;

6. Control your own trading risks and continuously enhance your learning awareness;

7. Follow the trend and operate self-discipline.

There are still some that I have definitely not noticed. Thanks again to the people who helped.