I remember the first time I was experimenting with Linux and decided to install Kali Linux (was still version 1 at the time) and in the process cleaned my hard drive. I was in first year and I hadn't been introduced to git, so you can imagine what happened to my code.

Or when I dumped all my databases into one SQL file (the feature looked tasty in phpmyadmin) and then after reinstalling everything, I couldn't import back the files.

Or last year, where I was on industrial attachment. So we were to delete some data from DHIS2 manually. So as a developer I grouped all organisation units to be deleted under one parent and wrote a python script to recursively delete anything in that group. Just when I was about to show my supervisor how efficiently my script was deleting stuff, he said, "Don't delete anything yet". I hope he doesn't read this *wink*

Fast forward, last week on Friday I dropped my external hard drive. It just works on one USB port now, no idea how and why.