If you know you will incur a loss if you sell your coins during crash then it is better to hold it and wait till the price go up to avoid such losses. While you still holding your coins even the price value is low, you still have no loss because it is still yours and has the possibility to increase again to gain profit.
Exactly, in crypto market, you have the option to sell or hold during crash. But again its totally upon the investor. So if a investor doesn't wants to take more risk he/she shall sell off few to whole of his holdings to reduce more loss if the crash continues as of now as its happening. Best would be to hold, but playing safe to sell off 30-50% and holding the rest can be beneficial and can turn out to be profitable.