The article linked below describes the 5 episodes that saw the value of Bitcoin (BTC) tumble. I knew about pretty much all of them though I did not know that in 2011 its value had gone from over 17 USD to just one penny (0.01 USD). We had a bad one in 2022 - and I am sure everyone in the crypto sphere is aware of how stressful and painful it was.
But one thing to note is that the crest from a few years ago become a new trough. That has been the pattern so far. Of course this pattern can not last indefinitely - but there is no indication that BTC (and crypto in general) is anywhere near its overall potential maximum. Hence even if things get tough I would think it prudent never to dump all the crypto you hold because even if a crypto has lost 70% of its value in the last week - and yes, I have seen even that - that doesn't mean it won't go back up in the coming days. Crypto may be the best investment ever over the long term - though, clearly, it does not come without pain and anguish.
References
Black Thursdays: Bitcoin's 5 Worst Crashes
Helene Braun, CoinDesk.com, 24 October 2022