Some potential choices ...
Run (Go to cash)
The problem is, how do you figure out how and when to get back in?
" . . . 'waiting for the dust to settle' is not a strategy, and neither is anything that is predicated on your ability to see into the future." (Well said Michael Batnick!)
An integral part of an effective plan is some way to manage risk. If your plan is to be 50% - 50% and one part of that 50% has gone way up, then arithmetic says you're not 50-50 any more. Maybe 60 40. Maybe 51-49. Etc. So periodic rebalancing taking you back to 50-50 can be used to maintain your risk management functionality.
Another not trivial advantage to rebalancing is it serves as a forcing mechanism to "buy low sell high." During the recent carnage, for example, if your stock allocation is now "too low," rebalancing will force you to buy more, i.e. "buying low."
Put some more cash to work (NOT a market call)
In nearly every other area of commerce, when something goes on sale that is a good time to buy. The psychology of investments among investors as a group might not always work that way. With that said, Blair makes an interesting point. If you are a long-term investor with cash on the sidelines, without agonizing over the impossibility of calling the single day that will be the "bottom," it might work out well long-term to put some of that cash to work.
Make a New Plan Stan
Somewhat euphemizing, Warren Buffet has a famous quote about finding out who is skinny-dipping when the tide goes out. Many people are conceptually happy with e.g. a 40% - 60% portfolio. We have had a very pleasant long run in stocks until recently. The "recency bias" means that, if you even actually experienced the last big drop, you don't remember very well how it felt. The one that just happened is all too painful and memorable. So while 40%-60% sounded like a good idea at the time, maybe your "true" risk tolerance is closer to 20% - 80%.
Also see ...
Also this ....
As I have previously written, while I don't give advice "off the cuff," I do offer a potentially, maybe, helpful phone conversation or maybe more than one without change, charge or obligation based on your interest level and after I have actually looked at the documents ...