Re: Welcome to the club!
"Lesson learned: NEVER decide to "clean up some old files" at 4:30 on a Friday afternoon. You WILL look for shortcuts and it WILL bite you on the ass."
Do not do anything of some significance on Friday. At all. Any major change, big operation, etc. must be made by Thursday at the latest, so in case of cock-up, you have the Friday (plus days week-end) to repair it.