The worst mistake was when i started off in the beginning and put a few bitcoin into an "investment site"
at first they pasi me , 0.01$% every hour for a few days , then suddenly the site was closed, i lost all my money.
Learned alot from that , still tried a few more but minimal amounts , some actually paid off!
Same here even I lost my bitcoins by investing into ponzi schemes like cloudmining and that was the worst mistake made by me, I wanted to multiply my bitcoins in quick time and at the end of the day I lost everything.