Typically this is good advise. Never chase a stock down.
Don't try to catch a falling knife and all that.

However on rare occasions the market sells off for reasons that are completely unrelated to fundamentals. The recent hedge fund deleveraging that we just experienced has been such an event and many stocks have collapsed for no reason other than cash needed to be raised and quickly.

Many stocks in the PM sector are priced as extreme bargains. If you can pick the right ones and be patient the gains could be enormous.