If you are talking about the cryptocurrency market then it is hard to predict the market so you cannot accurately know when to sell and when to hold. This is not like the stock market that some traders based on candle sticks or should i say technical analysis. Bitcoin is different it is very volatile, more volatile than the stock market. What i mean by this is that you cannot just simply rely on the news, if there  is going to be bad news then price will fall just like in the stocks. What i can suggest is to just put a target price, say if bitcoin falls to X amount you will be buying and if it gets to this amount you will be selling otherwise you will just hold. You'll be making more profit by doing that. Patience gets rewarded my friend.