The reason why is FOMO is bad sometimes because it leads to buy high sell low situation instead of buying low sell high that can lead to excessive loss which happened to me quite a bit during my early crypto days lol.
FOMO can be good (sometimes) but FOMOing on already 200% up projects can be bad IMO.
Often to happens when we are buying during the coins when seeing the price started to pump and if we tried to analyze it, definitely dumps will follow right after the surge. This scenario is not new to us, we already knew this since before. And it is a big mistake but somehow many were still not able to catch it and learn. That is why I'd never wanted to read the news, FUDs could start FOMO, and people started to get crazy once the drops started and immediately sell their cryptos.