Basically mine are pretty much similiar to most people here.

First is basically getting addicted to "martingaling". Where you think its not possible to get 20+ losses in a row. This is the worst feeling because every sequential bet is a huge loss to your balance and your heart just sinks if it rolls "red".

Second is also pretty common. Sometimes I manually set my bets and base bet sizes, so I do lots of manual clicking on the "Roll" button, however sometimes you move the mouse wrong and accidently hit "MAX BET" and you click Roll and its a loss. Hence why its a good idea never to keep all your BTC at your account.