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 don’t put your arm overhead
If you are in need of urgent money than selling is OKAY but for profit,
HODL is the best.
Best aproach in my opinion:
1. Pick the amount of capital you dont need.
2. Research and choose ~10 quality projects
3. Buy and hold them longterm
4. Don't even look at your portfolio for months.
Its almost certain that these quality picks will rise longterm and if you dont see the ups and downs you wont panic in the short term. So if you dont sell its almost guaranteed you will make some profit stress free.