I was about to say something like innkeeper said, safety with tube gear.
Having said that, I've been playing around with tubes since 15yo and I'm still alive, few shocks with up to 600V but a lightning in the boat did hurt much more, few hour staring at the finger where the discharge entered my body without being able to move it, few days without feeling anything with it.
In another forum we have a topic logging the shocks of the members, audio forum so a lot of tubes there, a few lightnings as well and some funny inductive kick backs (been there too)
As general rule, while working on live equipment probe around with one hand in the pocket, standing up with insulating footwear, once off check the caps are discharged and if not discharge them safely, having a dmm probe with an aligator clip on the other end, with 100k 2W resistor in between helps a lot, the other nice tool is a low-z mode on the EEVblog's BM235 but I didn't have that one when I was 15... Checking the voltage while discharging is nice, discharging too fast doesn't work as the charge builds bac up. On top of that, the usual mains safety precautions, those are quite a thread in it self, so be sure you know them to start with.
JS