The novice trader looks at the most successful of stock market moguls and wonders always what their secret is. Even those who have found great success in the markets themselves cannot always identify exactly what about them makes them a great trader, and endless magazine articles, books, and lectures have been produced exploring the subject. Usually, the explanation of the ideal trader boils down to one of four schools of thought, attempting to identify what outlook on yourself and the marketplace is the biggest indicator of success.
Psychological
Proponents of the psychological model argue that what is most important to the trading mind is that it be centered and rational. Great traders, this model claims, do not necessarily possess superior knowledge or methodology over their counterparts. Instead, these traders have a wisdom and focus to examine all aspects of the market impartially and objectively, allowing them to better asses risk management. Trading expertise, therefore, comes with improving yourself.
Scientific
The polar opposite of the Psychological model, scientific model advocates believe that the market can essentially be beaten Study and focus can pick out patterns and relationships in the market, and how these connections and cause-and-effect interactions change and evolve over time. Once the pattern is discovered, the marketplace inefficiencies it can be exploited for substantial gain. In the modern computer era, this model is often expanded to programming a model to identify and manage these inefficiencies automatically, removing any inconsistent human element entirely.
The Hidden Pattern
This model is somewhat similar to the scientific model, but with a bit less objective and a bit more art. These traders feel like that the market has a grand pattern that really does not change over time, even if they are not immediately obvious to the untrained observer. With great experience ones senses and interpretive abilities can be honed to identify these universal patterns when they appear and apply them to extract profit.
Performance
This group views trading as a sport, and the traders as the athletes. A successful trader can be broken down into several component aptitudes and skills, each of which can be focused on and trained much like taking free throws on a basketball court. Trading expertise, then, is a result of refining multiple skills to a razor edge so quick trading and decision-making is second nature.
The truth, as so often is the case, is probably somewhere in between. Each of the models has some sort of merit to its argument, and the best traders likely incorporate aspects of each in their work. By the same token, adherence to any of them would likely improve one as a trader and lead to greater results, simply because greater focus on either oneself or the markets is all but guaranteed to lead to greater understanding.

Perhaps the greatest indicator of success in a trader is not that he subscribes to one theory or another, but that he has discovered the outlook on the markets that best meshes with his outlook on the rest of life and reality. The man who is perpetually inwardly-focused in the rest of his life, focused on what he can do to conquer his troubles and get what he wants, will quickly become frustrated when searching for the unchanging patterns implicit in the marketplace, because that outlook takes out of his hands the power to change and grow. Similarly, he who believes every problem can be solved if only you had more information will never fully grasp a market philosophy that stresses guts and intuition, and success will evade him because of it.
The definition of success in trading, then, is carving out your own philosophy on the markets and pursuing it until success comes. The path to success is the path that speaks to you best.