Traders who lose focus. This focus can be the focus on the market or focus on themselves. Focus on their trading strategies, focus on their trading plan, etc.
While focusing on the market, a trader should know their capital, their strategies, risk-reward ratio, leverage, etc. Education helps in learning all of that. If a trader does not have proper education about the market, a trader fails to trade and profit. A demo account helps a trader learn too. If a trader does not practice on a demo account, a trader fails due to that reason, too. Focusing on oneself means focusing on one's emotions while trading. This is crucial, and if traders journal and observe, traders might be able to control their emotions in the right way.
If they do not focus on any of these, they lose.