FOMO
Fear Of Missing Out.
Like...when you're worried you're going to pass on the next Google. Or regret not joining your friends to go cow-tipping. (We suggest 20% if the cow is polite.) See: Bubble.
FOMO is sorta the first squawk from a penguin who senses a sea lion approaching. And the analogy applies to the investing world. A given stock is up 100% this year already; FOMO makes other momentum-driven investors pile in, and it doubles again. And maybe again. Until it doesn't.
And the poor schmucks holding the bad are...sorry. Like the penguin who was dinner.