I just have to say what a breath of fresh air this forum is, what with everyone else in the financial world doing Chicken Little impressions. Even Vanguard has these article links prominently placed about how you shouldn't panic, it's going to be okay, just keep your head, don't react with emotion, etc.
Regarding market timing, I fall into the camp of keeping an eye out for sales. I'm not going to time the market in terms of selling investments -- once I'm in, I'm in -- but I absolutely saw yesterday as a big fire sale, and I treated it accordingly. Yeah, I know, DCA, etc., and it's not like I sit on piles of cash for months, waiting for that one advantageous moment. But when I have money ready to invest, I watch the trends, and I pounce when those green numbers turn red during a correction. And if that doesn't happen, I shrug and buy anyway eventually.
So I won't time the market to sell assets, but I will do a little timing to buy. For instance, I'm considering making my Roth contributions next week if the prices stay low. If they don't, I'll probably hold off or spread them out over time. So far, this strategy has done quite well for me.
And if I end up missing out on an even better sale, I don't sweat it. It's a long game, not worth getting fussed about.