Let us not, in the pride of our superior knowledge, turn with contempt from the follies of our predecessors. The study of the errors into which great minds have fallen in the pursuit of truth can never be uninstructive.”
– Charles Mackay
Extraordinary Popular Delusions and the Madness of Crowds
A good read on investor psychology by John Hussman: https://www.hussmanfunds.com/comment/mmc171218/
Be careful not to blindly label every steep chart a bubble; it leads to sloppy thinking.
Just remember what the current stock market feels like with its low volatility and steady rises because this is what a bear market FEELS like (Video link):