When I found out about the bitcoin and started trading, I read the forums and there I saw the advice I follow: if the price falls, you either need to sell at the beginning of the fall or just HOLD
No it is not good to sell your bitcoin at the panic as selling at the fallen price call as panic selling which is not good choice at all, try to hold your bitcoin in any kind of situation so you will not get lose at all, if you see bitcoin price is getting down then use your patience and hold your bitcoin for long time no need to sell it fallen price, the other I would suggest you to do is try to buy as much as bitcoin you can buy for low price because after falling one price start to go high and it goes very high then.