By being flexible I mean that over time, your trading philosophy will undergo changes. These changes are brought about because of external events (economic considerations, natural disasters, political events, etc.), and because of internal events, usually my own mistakes.
My views change as economic, political, and technological changes occur both on and now off our planet. My views change as I see the market change. It is imperative that I be willing to change my thoughts and actions to meet new conditions. So, I am always looking to adapt my trading to the market conditions. Example: In recent years, markets failed to trend as long and as far as they used to. These days, primarily because of computerized trading, markets tend to swing between perceived over and under valuation. If I hadn't adapted to this reality, I would long ago have lost my money and probably would no longer be trading.