However you need to adopt a trading strategy. DO not be greedy. Set a goal. As soon as you achieve it, cash out your capital, keep your profit, smile to the bank and reinvest.
It's really hard to set a goal at trading.
If you are a professional trader, you should know that sometimes the company/coin that you invested in are publishing news or having something new going, it's hard to determine from upfront when it will be the right time to sell.
Greediness at trading is a thing that happens only to unprofessional traders, they tend to fall for feelings and to trade ( just by how they feel), while professional traders will ONLY trade based on technical analysis and other technical factor.
A professional trader will never buy and sell based on feelings!