The majority always loses

If a betting game among a certain number of participants is played long enough, eventually one player will have all the money. If there is any skill involved, it will accelerate the process of concentrating all the stakes in a few hands.

Something like this happens in the stock market.

There is a persistent overall tendency for equity to flow from the many to the few.

In the long run, the majority loses.

The implication for the trader is that to win you have to act like the minority. If you bring normal human habits and tendencies to trading, you will gravitate toward the majority and inevitably lose.