Melt-ups often precede melt-downs.

MELT-UP: a sustained improvement in the investment performance of an asset, driven partly by a stampede of investors who don’t want to miss out on its rise, rather than by fundamental improvements in the economy.

https://www.investopedia.com/terms/m/melt-up.asp

…………… Gains that a melt-up creates are considered to be unreliable indications of the direction the market is ultimately headed. Melt ups often precede meltdowns.

h/t  mark000