The question itself is the answer
PANIC.
Everyone knows cryptocurrency market is highly volatile and risky.
And most of the people do emotional trading.
They sell when it is crashing. And suffer from the loss. They panic and sell in the loss.
What is the point in selling at low?
One must wait for the market to turn green and bullish.
The way to stop the panic is to not engage in panic-inducing activities such as day trading.
It is like the old joke; a man goes to the doctor and says my arm hurts when I put it overhead.
The doctor says dont put your arm overhead

If you are in need of urgent money than selling is OKAY but for profit,
HODL is the best.
Actually it can be our own control, do not be too afraid if there is a decrease in the price of coins, marenas where may the coins are down continuously, there must be times to rise as well, never affected by the market movement, because it is a big investor trick.