Always good advice, that. In particular, try to know yourself well enough to avoid falling victim to the Dunning-Kruger effect, from either side.
One thing I've frequently been heard to say is that I know just enough about working with natural gas to know I don't know enough about working with it to be safe. This is, from a distant perspective, probably untrue, not least because I know enough to be cautious. Sadly, whoever was responsible for much previous gas work in this house was a victim of the effect from the low side; he didn't know to seal threads, which almost led to the house burning down before we moved in, and it turns out he didn't know enough to realise that gas hardware and water hardware are Not The Same Thing, despite both working on pipes.
I would love it if the gas standard became left-hand threads. That would make gas line idiot-resistant, in many ways.