The expectancy gap and performance leaks

When trading, you are free to construct your own methodology and set of rules to use - what markets to trade, triggers for entries and exits, how much equity to risk etc. That's the easy part.
 
For the majority of us, the difficult bit is ensuring you keep operating within that framework.

Building your own approach to the markets and the decisions and actions you take are entirely within your own control. But you have no control over what the markets do. Ideally, you want to react to the market's price movements, and trade within the confines of your carefully constructed framework.