My dad advised me to put some money into stocks around 2004 or so, specifically suggested Lloyds bank on the grounds that "if they went bankrupt we have bigger problems".
Then the global financial crisis happened.
The LLOY share price has still not recovered to the price I bought them at. Thanks to share dilution during the GFC, even inflation probably won't bring the price back to the level I paid for them by the time I reach current mean life expectancy.
Most of them have now committed to simple dollar-cost averaging against broad index funds like VT.
It's a lot harder to shoot yourself in the foot with that attitude.