Working on hot wires is no problem. Ground wires scare me and I'll turn off the main breaker before I touch them. You can never be sure what ground is really at.
In more than a few dilapidated rentals I've been in...
Ground is ... all the metal bits in the bathroom and there's earth leakage happening somewhere.
The safe work procedure is then: get the shower to the desired pressure and temperature before you get in / while you're still wearing your shoes then try not to touch the taps while you're in there.
But don't tell the guests cos hearing them yell "FUUUUCK!" is amusing.
Bonus points if they pass out from the shock and knock their head on the way down.
