super-oops with computers
The worst computer mistake I ever made was on my C64, way back when I had only one floppy drive. I wanted to make a backup copy of a disk, & the disk copying program I was using had to format the backup first. It was halfway done with the format phase when I realized I was holding the blank floppy in my hand and that the disk I wanted to copy was being formatted.
super-oops with computers
@arielmt oh no!
super-oops with computers
@arielmt I remember, when I first installed Windows 3.1, I thought I could delete all my files from DOS, because now they were in Windows!
super-oops with computers
@Tobi I think I did one worse. I tried booting Windows 1.01 floppies on the family Tandy 1000, but Windows kept stopping, complaining about something DOS-related. I looked on the disk & decided that it wanted me to delete msdos.exe, completely ignorant of the fact it was the Windows shell (MS-DOS Executive) & not a bad or rogue DOS kernel.
super-oops with computers
@arielmt Oh no 😅
super-oops with computers
@arielmt Good habit!
But what about USB flash drives? 
super-oops with computers
@Tobi *an ominous 'is the villain really banished' musical sting*
super-oops with computers
The lesson I took away from that mistake was to write-protect the source disk before thinking of starting a copy.
That force of habit is still with me today. If I format, image, or copy anything & have more than one SD card involved (including micro-SDs in SD dongles), I flip the tab to "Lock" on the source card.