"The Disciplined Trader: Developing Winning Attitudes" by Mark Douglas, published in 1990, is a foundational work in the field of trading psychology. This book addresses the often-overlooked psychological aspects of trading, focusing on how a trader's mindset can significantly influence their performance in the financial markets.

Mark Douglas emphasizes that successful trading requires more than just a good strategy; it necessitates a disciplined mental approach. The book explores the emotional and psychological challenges that traders face, such as fear, greed, and the difficulty of maintaining objectivity. Douglas argues that these psychological barriers can prevent traders from making rational decisions and adhering to their trading plans.

Key concepts in "The Disciplined Trader" include:

1. Understanding Market Realities: Douglas explains that traders must align their perceptions with market realities, recognizing that markets are inherently unpredictable and that losses are a natural part of trading.
2. Developing Self-Discipline: The book emphasizes the importance of self-discipline in sticking to a trading plan, managing risk, and controlling emotions. Douglas provides practical techniques for building and maintaining this discipline.
3. Emotional Control: Douglas discusses how emotions can cloud judgment and lead to impulsive decisions. He offers strategies for managing emotions, such as staying detached from individual trades and focusing on long-term performance.
4. Building a Positive Attitude: The book highlights the importance of maintaining a positive and realistic attitude towards trading, which involves setting achievable goals, learning from mistakes, and staying motivated despite setbacks.

"The Disciplined Trader" is praised for its practical advice and clear insights into the mental challenges of trading. By addressing the psychological side of trading, Douglas helps traders develop the mental toughness needed to succeed in the highly competitive and often stressful environment of financial markets.

Overall, "The Disciplined Trader" is considered an essential read for anyone looking to improve their trading performance by mastering their mindset and developing a disciplined, consistent approach to the markets.