The main lesson is to understand the market, to know in which direction it goes, in what phase we are, why are we there, technical analysis? Fundamental? both fail, the main thing is to understand the market and only understand studying books, such as Wyckoff, Livermore, who were first-rate speculators, also Buffet who is a sensational investor.
You have a good point! If we can only fully understand the market then we can know the right time to enter and to exit in trading. There are many information around the internet that are useful in trading of cryptocurrencies.