So I was implementing a password manager for the very first time.
For every single account I had, I created a new password within the password manager, and copied it with ctrl+c
Then I went to "change password" in the online account and pasted the "new password" in with middle-click.
For. Every. Single. Account.
The next day I couldn't log into anything and of course had no idea what string I had replaced all my passwords with.
Getting back into my main e-mail account was a bitch, cause I had set it up with my home phone number and address in the year 2004, never updated that info, and moved 11 times since then.