Someone once told me: "always have a few limit orders, in the background, at prices you don't think you'll ever see."
The point of this message is that, every once in a while, a flash crash, drop or panic does indeed hit the market.
And if you have a few orders running in the background, you may get lucky.
Remember, these are not 1% drop orders. These are 10% drops, 20% drops, and more. Heck, I have a limit order on Apple at 99/share... maybe one day, you never know.
The key to this tactic is that there's no downside to placing a limit order like this... if it hits, you got lucky. If it never hits, you did not really risk anything.
Anyways, I saw the dip in Ethereum tonight, a cool $200+ per ETH in a matter of minutes. I'm sure someone had a bid hanging out at those levels.
I guess that's the thing about this lesson, place that limit order VERY low and just wait.