Cringiest mistakes starting out?

I'm 17 years in my chosen career this year and randomly remembered a really embarrassing moment on my first day starting out as an office assistant in a solicitors office. I was 16, and really trying to impress in my summer job. I was given the task of bringing over the DX post to the exchange place. When I got there, I saw a box with the name of the firm I was working in on it and shoved all the envelopes into that box.

Managing partner was spitting fire the following morning when all of our DX post from the previous day was returned to us. Instead of landing me in it, the girls in the office covered for me and said someone must have made a mistake in the DX place.

I still cringe whenever I think about it and dunno why it popped into my head this Monday midday.

So please, make me feel better and tell me yours!