If you trade for a while, you will see a lot of rules lists. These are basically list of rules traders put together to, bluntly stated, not screw up like they did in the past.
There is a lot of overlap among rule lists, and frankly most of them aren't worth much. Particularly in cases where the list spans dozens of different rules (on reading these, one can conclude the writer of the list has made a glittering variety of errors that he believes he can circumvent if only he has a long enough set of rules to follow).
I've got my own list, but it is short and sweet. Like all rules writers, I do my fair share of ignoring some of these from time to time, and virtually every time I do, I regret it. I have gone to the length of having the inside and outside of my laptop computer emblazoned with these three rules. Maybe I should do the insides of my eyelids as well.
It has cost me a huge amount of money to formulate these "trading laws", if you will, and I offer them up - as I do everything on this blog - for free, with the hope that it will help some of you. If one day I can follow these three rules absolutely consistently, I'll be a much better trader for it.
There are rare occasions when I do think ignoring those last two rules is OK, and that is during truly extraordinary market events. Let's say you've got a large position on index puts going into a new trading day, and for whatever reason the market is going to gap tremendously lower at a key support level (which could be a Fibonacci, a horizontal line, or what have you).
In an instance like that, I see nothing wrong with doing a close immediately at the open, because in extreme cases (like when the Dow opens down 400 points), fear is usually greatest at the open. But by "extraordinary" I mean "extraordinary" - - not once a week. The bottom line is that 99% of the time, I do not stray from these rules.