I once messed up a routine server update without doing a backup first. It froze in the middle the and an entire school district lost access to their email. My boss graciously took the angry phone calls and I stayed up all night learning how to rebuild the mail server from various online documentation. I finally got it back up and running with messages restored.
The only thing that my boss said when he came in the next morning was, “Now you know why I stress the importance of backing up before every update, no matter how small. I trust you’ll never make a mistake like that again.”
He was right. I’m now a fanatic about backing up. My failure got me to institute a process that I’ll rely on for the rest of my life.