Oh! Yes, I feel that ouch through the computer screen, but of course it is 20/20 vision in hindsight for us all in life.
I have slowly accumulated since 2003 and never sold. I had to split it with my idiot X Asshat cowardly cheating hubby in 2017 upon divorce but still never sold one share and bought a bunch more when it was in the toilet over the last year or so.
I saw my X did sell ALL of his when it dropped (I still have legitimate access to our old joint account and all his stuff is still there--I am sure he hasn't considered at all that I can see everything--that is a huge reason I left that brokerage myself!). He did exactly the wrong thing and sold off all of the AAPL as it was on the skid, then bought quite a bit of it back a few weeks later as it bounced off the bottom. His foolishness locked in losses of over $87,000 for himself on that one move plus triggered a tax bill that would have shriveled my brain.
I remember during other drops from Brexit or the Asian Flu or whatever 3-day long phony drama issue of the moment was he would pace through the living room pulling his hair --literally pulling on his hair-- and say "We can't have capital erosion! We should sell!" and I would tell him to chill because we don't need the money and we would stay the course for the inevitable rebound. So now he is on his own and he is screwing it up. In summary, he is $125,000 down in value in the last 12 months because he is playing games and trying to time the market, always selling low and buying high with his latest freak out or hitting some click-bait stock name that slumps after he buys it. He is $125K down when he should be about $300K up on this big year.
Yes, it is bitter Schadenfreude to watch him act so recklessly but he is sooooo not my problem. I have realized over the last 2 years that I always assigned qualities and character to him that simply were not there and money savvy was one of them-- my 20/20 vision on that has been quite a wake up.