Hi Guys,
Thank you all for your enthusiastic replies. I appreciate all of them for their prospective and for their civility.
I believe we all invest with constraints; with some self-imposed set of rules that act as speed governors to control potentially disastrous behavioral biases.
As Dirty Harry remarked in that film series: “A Good Man Always Has to Know His Limitations”. Here is a Link to that terrific scene:

I think good investors do either formally or informally generate a set of operational rules. These rules guide them in making investment decisions.
The rules need not be inflexible and forever cast in stone. Strong adherence to the rules is mostly necessary since frequent violations defeat their purpose. But market circumstances and personal circumstances change, and the final rule should be that change is permissible under evolving conditions. There is much art and just a little science that should dictate when these changes are warranted.
The constraints suggested in the referenced article are not a bad point of departure. Personally, I follow many of them, but definitely not all. Each of you guys likely follow a different subset that more closely defines your own investment philosophy, style, time horizon, financial know-how, and special proclivities.
All of us see investing from differing perspectives. What’s significant to you might be trivial to me. Professional firms follow their own shining guidelines. As a grand illustration, allow me to reference a seminal position paper by Oaktree’s Howard Marks. The paper is titled “The Most Important Thing”. Here is the Link:
http://www.oaktreecapital.com/MemoTree/Most Important Thing (070103).pdf
I hope you find his summary as informative as I did. I love adding some extra value to these exchanges. Enjoy the Marks philosophy.
Marks simply could not consolidate his “most important thing” to a single item. He lists quite a few. When investing there is almost never a single best approach, and any best approach will surely morph over time. Like Marks said: “There are a lot of moving parts in this machine, and many of them are beyond our control.” So both control elements and open-mindedness are essential ingredients for success.
Best Regards.
ADDED COMMENT: The Howard Marks Link is not working on this site. Try this address:
http://www.oaktreecapital.com/memo.aspxAnd then click on the 2003 memos for access to the referenced article. Sorry about the problem.