When everyone is buying, you feel the urge to buy.
When everyone is selling, you feel the urge to sell.

This isn't a coincidence. It's the herd effect, one of the most studied mechanisms in behavioral finance.

The problem is that most traders act at the wrong time: they buy at the peak of euphoria and sell at the bottom of panic.

The market doesn't reward those who follow the crowd. It rewards those who think before it.