yep, if you are in for the long term. Buy aggressively on big down days. That last thing you want to do is sell.
Now it would be smart to sell something today, if you have wanted to do so recently. Take a little of the table if you no longer believe in that particular stock or mutual fund. Just dollar cost average your 401K dollars, and max in your contributions. Really bad markets are a gift if you have decades to invest.