Hey there!
A question of panic selling was already discussed on this forum a billion times. But whats bad here? If you are sure that the price will grow back then you can just buy some BTC in better rates. The more dangerous will be the situation when someone is buying BTC while being afraid of loosing some profits despite the fact that pump has already happened (I'm calling it a panic buying). Thats seems like a straight way to lose money and make a bubble.
Yes.That's really a dangerous aspect in trading and i too have suffered a lot because of buying a pumped coin and losing out by selling it at very low rate when it immediately gets dumped.I happens frequently in altcoin trading where mostly altcoins get pumped and dumped.