What was your “aha” moment when it came to understanding the stock market?

What was your “aha” moment when it came to understanding the stock market? Any good nuggets of wisdom to share? One of mine is that investor psychology is largely responsible for short term stock prices. When people were panic selling during March 2020 in the early pandemic I bought a lot of stocks that all made money since. A great bit of advice I read was “don't just do something, sit there!”