I think that the main thing is not to start panicking! It is the most important rule for traders in any situation. To my mind, everyone should understand the basic rules of market and not to hurry to sell coins at the low price
Everybody knows about it, but each time, when the price is falling, most of the traders and investors start to panic. I suppose, the main thing that you have to do when you feel a stress is to stop and wait not to make a fatal mistake.