my worst mistake that i made with my bitcoin was gambling them. because no matter what i do i always end up losing without any profit.
I would add that dice is a big mistake. It is tempting to think you can make some money using some derivative of the Martingale system and it will work for awhile but eventually you will get wiped out.
The worst mistake that i did was investing in a hyip website (it was cloud mining) and got scammed at the end.