Well, you have to be prepared for it. Look at the way Haejin tries to reckon with several possibilities always, have to bring yourself into position at your exchange so you can act fast and decisively in the opposite direction - and read up on what the analysts say so you can decide what to do.
Or get into a rather stable currency to stay out of the fire, like litecoin, or even flee into tether or fiat for awhile ;)