In my opinion, the best time to sell is when the market price of the coin is 20%+ higher than the market price at which you bought the coin. Dont wait till the market price is 95%+ before you sell. That only happens when you got your eyes glues to your machine 24/7. Dont be greedy... Make a little profit and grow it over time. Cryptomarket is growing and full of terror! Be careful
Yes you should not be greedy because the market is depending on supply and demand so you will not be always earning profit in the market, invest only a value that you are capable of losing that is the reason you should not be greedy on cryptocurrency.