Jeff Aronson warns that prolonged success breeds dangerous overconfidence. When an investor is on a hot streak and feels they can do no wrong, their perception of risk becomes warped. This psychological shift, where they think "I must be good," is precisely when underlying risk is escalating, not diminishing.

Simply keeping pace with peers is not a valid measure of success. If peers are taking excessive risks in a bubble, matching their performance means you were equally foolish. True skill is outperforming in bad times while keeping pace in good times.

During due diligence, it's crucial to look beyond returns. Top allocators analyze a manager's decision-making process, not just the outcome. They penalize managers who were “right for the wrong reasons” (luck) and give credit to those who were “wrong for the right reasons” (good process, bad luck).

While a pension fund's ultimate goal is hitting its absolute actuarial return, this is irrelevant for short-term evaluation. In the short run, performance must be judged relative to peers or benchmarks to account for the prevailing market environment.

During periods of intense market euphoria, investors with experience of past downturns are at a disadvantage. Their knowledge of how bubbles burst makes them cautious, causing them to underperform those who have only seen markets rebound, reinforcing a dangerous cycle of overconfidence.

Investors often judge investments over three to five years, a statistically meaningless timeframe. Academic research suggests it requires approximately 64 years of performance data to know with confidence whether an active manager's outperformance is due to genuine skill (alpha) or simply luck, highlighting the folly of short-term evaluation.

Timing is more critical than talent. An investor who beat the market by 5% annually from 1960-1980 made less than an investor who underperformed by 5% from 1980-2000. This illustrates how the macro environment and the starting point of an investment journey can have a far greater impact on absolute returns than individual stock-picking skill.

Investors rarely sell a fund for outperforming its benchmark too aggressively, but they should consider it. Research by Vanguard's John Bogle tracked the top 20 funds of each decade and found they almost always became significant underperformers in the following decade, demonstrating the danger of chasing past winners.

Even long-term winning funds will likely underperform their benchmarks in about half of all years. A Vanguard study of funds that beat the market over 15 years found 94% of them still underperformed in at least five of those years. This means selling based on a few years of poor returns is a flawed strategy.