Not just BNB has dropped 50%, many coins in the market were also down. Well don't worry I believe the potential of BNB, it will increase in the future for sure, just keep holding.
Surely what is happening to bitcoin affected most of the altcoins. Bnb is not different. Hodlers shouldn't panick because of this. Bitcoin is soon gearing for highs by 2020 and most valuable coins will start trading on highs too.