As someone who has hung out in Reddit's personal finance areas for many years now, the paniced posts of March 2020 and in 2022 were very real. Lots of climbing people down from the ledge during those time periods.
Many folks realized that they may be more risk adverse than they thought. (And those were relatively short bursts: if the things had headed down for months (or longer) there would be much more sleepless nights for many people.)
Those were just minor blips. 2020 was a very short-lived dip of less than 30% and 2022 was a bit more sustained drop of ~35%.
The dot.com bust was an actual legit crash, at almost 85% drop.
I'd suggest at current valuations we need to be prepared for a crash at least as significant as that.
That is very true and a trap that is important to be aware of. Anyone who started investing after ~2010 has only ever experience a bull market, so expect severe pain at some point. It doesn't go up forever.
I'm old enough that my investing history inclused the dot.com implosion that wiped out nearly all of everything, and also the financial crisis of 2008. It remains true that investing in the winning companies is by far the best return by orders of magnitude.