"Retail investors" mistakenly believe that trading is a "zero-sum game"

They believe that the money they make is the money others lose; and the money they lose must be the same amount that others have earned. When they lose money, they are filled with resentment towards those who make money — which is actually resentment they have brought upon themselves...

They completely overlook the greatest force in the trading market: economic cycles, also known as bull and bear markets. In a bull market, the vast majority of people make money, while the losses of a few cannot compare to the gains of so many; in a bear market, the vast majority of people lose money, and the losses of many are many times the gains of a few.

So, this is not a "zero-sum game" at all. If you lose money, the correct explanation is: the timing of your purchase was wrong.