I set my failure or loss by waiting for the price to go down and after that buy it again at the right moment or the right moment because the price will definitely go back up, and preferably trading do not use all the money there, you put money to overcome this loss.
The only possible way of managing the potential loss during crash is to keep trying your luck in the future too. The market value keeps on changing most of the times and that you actually need to target the market at the right time and before doing that, you also need to have some plan in your mind. Get into the market at time when the market value is falling down and then stay over there till the time its value rises high.