I'm comfortable working live circuits I know, the routine stuff I've done a hundred times. But when I open a panel that's been damaged, or one where nobody can tell me if it's really dead, my hands go cold. I keep thinking about all the ways a system I can't read could still be holding a charge.
More people experience this than they realize.
You handle familiar high voltage fine, but the damaged and unknown ones still scare you.
If this sounds familiar, the Library can help you find the bigger picture.