I did something worst many years ago: I was working for a regional ISP and during a major incident, I had to reroute traffic through a different path. Under big pressure, I did the infamous Cisco mistake "switchport trunk allowed vlan 50" instead that "switchport trunk allowed add vlan 50" and I locked out myself and all the customer from our broadband customers. We had to call a DC technician and ask him to share a console through a local console server.

Lesson learned: even if you are under big pressure take your time to plan and review the modification 15 minutes can save hours.