Tim Guinness's firm uses 30 equal-weighted stocks to diversify risk. This forces a "one-in, one-out" policy, compelling the team to sell their least-favored holding to add a new one, thus overcoming the common investor weakness of being poor at selling.

The "Liking-Loving Tendency" causes investors to identify personally with their holdings. They ignore faults, favor associated things, and distort facts to maintain positive feelings. This emotional attachment leads them to rationalize bad news and hold deteriorating assets for too long, destroying capital.

Post-mortems of bad investments reveal the cause is never a calculation error but always a psychological bias or emotional trap. Sequoia catalogs ~40 of these, including failing to separate the emotional 'thrill of the chase' from the clinical, objective assessment required for sound decision-making.

Private equity managers often get psychologically anchored to their purchase price. Instead of cutting losses on a poorly performing asset to redeploy time and capital, they hold on in the vain hope of getting their money back, turning a bad deal into a time-consuming, mediocre one.

To avoid emotional, performance-chasing mistakes, write down your selling criteria in advance and intentionally exclude recent performance from the list. This forces a focus on more rational reasons, such as a broken investment thesis, manager changes, excessive fees, or shifting personal goals, thereby preventing reactionary decisions based on market noise.

Short-term performance pressure forces fund managers to sell underperforming stocks, creating a self-fulfilling prophecy of price declines. Investors with permanent capital have a structural advantage, as they can hold through this volatility and even buy into the weakness created by others' behavioral constraints.

A Wall Street Journal experiment pitted a monkey throwing darts at a stock list against professional traders. Over a ten-year span, the monkey's long-term, passive 'buy-and-hold' strategy won. This demonstrates the power of long-term investing over short-term, active trading.

Corporate leaders are incentivized and wired to pursue growth through acquisition, constantly getting bigger. However, they consistently fail at the strategically crucial, but less glamorous, task of divesting assets at the right time, often holding on until value has significantly eroded.

Suboptimal selling is often driven by fear: a position gets "too big" or you want to lock in gains. A better approach is to only sell when you find a new investment you "love" more. This forces a positive, opportunity-cost framework rather than a negative, fear-based one, letting winners run.