There are many old, "ageless" lessons in investment world which can be applied to the crypto area, too. With the difference that by cryptos the volatility is much higher, the movements, bigger.
For example in the technician school (chartists), they say, you should let gains grow higher and cut losses. Therefore, they use automatic stoploss-orders to cash out if prices turn down.
Others say, "“Fearful when others are greedy and greedy when others are fearful.” (Warren Buffet). Buy if all are selling and sell if all others are buying.
I like more the second option. But only if the asset has stable fundamental value. That is very difficult to determinate in case of cryptos.
RE: 3 life lessons from the flunctuating crypto market