The markets are falling and that is good news for a systematic buyer, someone who is slowly building a portfolio for his retirement. First, it opens the range of available stocks because after the drop they are within the chosen parameters (P/E, dividend yield...), and second, he can buy more shares using the same amount of money.

This person in general is not thinking of selling, so it doesn't matter if on paper his portfolio is worth much less. It only matters the companies' health and the dividends they pay.

In any case it is difficult for non professional traders to isolate themselves from the tough environment. Also it is fundamental to stick to the plan every investor should have before confronting the markets.