A framework book on the psychological mistakes that undermine investment execution and lead to poor returns, grounded in seven years of real-world return data from top fund managers deploying $25–150 million. The core idea is that a sound investing strategy is not enough—execution of that strategy materially drives outcomes. How investors manage positions after making an investment matters more than prediction accuracy. It’s not just how often they’re right, but how they manage their winners and losers that has an outsized impact on returns.