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
You should be greedy depending on the market situation and the price right now is very low so you should invest a huge amount in order to take advantage of the current situation.