Treating investment principles as inviolable laws rather than flexible guidelines will yield better results

For investors, there’s no external enforcer of rules, so it comes down to self-discipline. There may be situations where deviating from the basic tenets of sound investing could have led to better returns. However, these exceptions are few and far between and can typically only be identified with certainty in hindsight. So it’s much better to regard these guidelines as sacrosanct.