A well-documented pattern in behavioral finance, and a specific one worth recognizing in your own trading.
Herd mentality is the tendency to follow what a large group of other traders or investors are doing, rather than an independent read of a setup, driven by the discomfort of being the only one positioned differently from the crowd.
There's a real social and psychological comfort in a losing position that "everyone" was in, versus a losing position that was uniquely yours. That asymmetry pushes traders toward crowded trades even when their own analysis would have pointed somewhere else, since following the herd distributes the discomfort of being wrong rather than concentrating it.
PnL App logs the decisions behind every trade, so a bias like this one shows up as a real, measurable pattern instead of a feeling you can rationalize away.