Time now to observe two of the most solemn anniversaries in the investor’s calendar. March 9 marks five years since the Dow plunged to its lowest point of the past 17 years, in the dismal pit of the financial crisis. March 10 is 14 years since Nasdaq levitated to its all-time high in the sparkling delirium of the Internet bubble. It seems March Madness happens on Wall Street too.

The anniversaries are solemn because they mark the two days of the past 50 years when we investors most urgently should have taken action, and of course hardly any of us did. On March 9, 2009, we all should have broken our kids’ piggy banks and bought pretty much anything. GE was $7 (recent price: $26); J.P. Morgan Chase was $16 (recently $58); an S&P index fund is up 170%. And on March 10, 2000, we should have sold or shorted every technology stock on the planet. Even a major player like Cisco had doubled in the prior six months, and it then lost 80% of its value the following year; lesser companies went to zero.

Not that we had to bet the farm on those exact days. Just coming close with some modest portion of our investments could have yielded spectacular results. Yet we didn’t. So why not?

The answer is not mysterious. The findings of behavioral finance reveal how we’re hardwired to make these blunders and why avoiding them requires nearly superhuman discipline. Over the eons we’ve evolved four tendencies that conspire to sabotage our investing decisions at critical moments: