Real professionals are ofc selling when the price is high and buying when the price is low but to know when which level of investment is necessary is complicated in the best of times and the blockchain/crypto-currency market is still way too volatile and "new" to get through by using basic stock market knowledge. Problem is ofc, every action by every single investor influences everyone else - it's a bit like a soft version of the prisoner's dilemma: If no one sells, it is good for you to also not sell, but if a lot of people sell, you want to be one of those....so you need to trust either 1) "the market" ...hard...or 2) the long-term-correction-tendency. To be fair, a good investment won't be underrated for long but trusting the market in general - especially on the short term - is....brave.