rule #1Never, ever, under any circumstance, should one add to a...

rule #1
Never, ever, under any circumstance, should one add to a losing position ... not EVER!
Averaging down into a losing trade is the only thing that will assuredly take you out of the investment business. This is what took LTCM out. This is what took Barings Brothers out; this is what took Sumitomo Copper out, and this is what takes most losing investors out. The only thing that can happen to you when you average down into a long position (or up into a short position) is that your net worth must decline. Oh, it may turn around eventually and your decision to average down may be proven fortuitous, but for every example of fortune shining we can give an example of fortune turning bleak and deadly.

Source:
Dennis Gartman's Rules of Trading.

The "Not-So-Simple" (But Really Utterly So) Rules of Trading