In the realm of trading psychology, discipline refers to the ability of an investor or trader to adhere to a predetermined trading plan or strategy, regardless of emotional impulses that might suggest otherwise. It means making trading decisions logically, based on established rules, rather than erratically, based on fleeting emotions such as fear, greed or excitement.

A disciplined trader does not allow short-term market fluctuations to deviate them from their long-term investing game plan. They understand that the market will often behave unpredictably, and accept this as part of the trading environment. The key to successful trading lies not in predicting these movements, but in consistent and thoughtful reaction to them.

Furthermore, discipline includes the ability to take losses without panicking, and to realize profits without becoming greedy. It also entails maintaining sound money management tactics, such as setting stop-loss orders and diversifying portfolios, in order to protect assets.

Overall, discipline is an essential trait for successful trading and a critical part of trading psychology. Without discipline, even the most effective trading strategy can fail. Hence, successful traders prioritize cultivating discipline as a necessary trading skill.