James O'Shaughnessy — American Businessman born on May 24, 1960,

James Patrick O'Shaughnessy is an American investor and the founder, chairman, and CEO of O'Shaughnessy Asset Management, LLC, an asset management firm headquartered in Stamford, Connecticut... (wikipedia)

If you look back to the most spectacular blow ups in history, you can always tie them to a couple things: They were extraordinary complicated strategies that maybe even the practitioners themselves didn't understand, and they were overleveraged.
Fear, greed and hope have destroyed more portfolio value than any recession or depression we have ever been through.
If you are an investor who's retired and hopes to live off the income that your portfolio is generating, then we would focus just on the dividend yield.
By relying on the statistical information rather than a gut feeling, you allow the data to lead you to be in the right place at the right time. To remain as emotionally free from the hurly burley of the here and now is one of the only ways to succeed.
It seems that the one thing that doesn't change is people's reaction to short-term conditions and their axiomatic ability to perpetuate them far into the future.