To plagiarize an adroit investor from another forum; that would just be a RBD (really bad day). I would consider that a rare opportunity to buy a lot at a discount. I would not sell and would buy, buy, buy, then say bye, bye, bye to my employer, probably earlier than I had planned, however, you never know where the top or bottom will be. I have much faith in our system surviving and I base my investments on that. Since I am in the accumulating phase, the lower the market drops, the better I feel because I invest monthly, sometimes more. Yes, it's nice to see the account balances growing daily for many months, but the flip side is that I am paying Neiman Marcus prices for Target funds. No easier answer here.
As an example, I have accumulated mid 5 figures in cash (0.2% interest account) waiting for a RBD but if I had invested it 6+ months ago, I would be up more than 10% based on earnings in other index funds over the same time frame - so I lost big time on my market timing plan = super fail.
Only hindsight can be your reliable guide.
If anything, as I've heard before, buy when everyone else is panicking and sell when they are cocky, or something much more eloquent than that.
Happy Holidays!!!