In occasion like bitfinex hack, you have to act fast if that type of event cause panic to traders and market get dumped. Sell when market is having heavy selling pressure and quickly buy back when price stabilizes.
We really could convert or put up money into bitcoin anytime . As you mentioned we should be aware always regarding on its movement so that we could able to avoid so much loss when there are unpleasant circumstances that might possible happen on bitcoins price that would cause to dump. If you saw that there are panic selling it would be really depend on you if you decide to sell off too or decide to hold and wait for the bitcoins price to rise up again. Any investment do have risk.