The worst mistake that i do in my trading experiences is when im getting greed when using margin trading i get a profit about x20 - x30 using margin trading on poloniex when xrp and str are in the bull run my 0.08Btc turned into 4Btc just within a few months but im so greedy that's why i margin more coins to get more profit but my mistake are i didn't close my position early so when str and xrp gets dumped i lost about 50% of my profits but it's not so bad because still i have a good profit so i learned a lesson when you're in trading don't put all of your capital into 1 - 2 coins.