One of the reasons why traders loose money everyday in their trading is 'greed'. A trader will hear about a particular coins he wouldn't even do research or proper findings to know the future of the coins which he wants to trade his money on but rather the greed in the trader will push him to use all he has with the aim of making 4 or 5 times of his trading capital.
Traders are big risk takers so everyone should know what he or she is trading on so that when you loose which is normal, you will learn more.
No trader is perfect but mastering coins you trade on can help you, remember trading is like a gamble you either gain or loose.
Do not trade with everything you have,your egg can not be save in one basket, I have lost but I have gained more in trading with the help of research and mentorship programs.
I think the real problem is putting all your eggs into one basket rather than being greedy. Although putting every egg into a single basket could be seen as the result of greed. Its obviously important to diversify your investments into things worth investing into. I for one would never invest into start ups which do not even have a institutional investor behind them.
I remember someone once did an experiment and randomly invested into whatever came up first and that person did remarkably well. So there is obviously a limit to how much research will be useful.