Fun story! A long time ago I interned for a very large catalog company. It was my first real internship in IT.
One of the first things (so a couple days in, not exactly day one) the CTO had me do was "map" their server room (e.g. figure out where data and power cables were going to and coming from, physically and virtually). While working my way through the back of a massive UPS rack, I stepped on one power cord that happened to traverse over another 10 or 15 cords. I did it in such a way that all of those cords were pulled ever so slightly from their UPS connections. I didn't even realize it until one of the staff IT guys came in the room a few minutes later and asked me what happened. Turns out those cords powered the 300+ Citrix thin clients in use by the national call center downstairs.
I thought for sure I was in huge trouble, but everything came back online fine, the staff IT guys poked some fun at me and the CTO helped turn it in to a valuable lesson. I learned a lot of great stuff during that interneship and to this day, 15 or so years later, I still think of that experience when doing risky work (or when I fuck it up).