There is a saying that "experience is the worst teacher, test comes first before the lesson".
This is true in every aspect. In electrical engineering design, earthing or grounding is almost always the least concern of designers and installers. It is a safety measure mostly taken for granted as the benefits of earthing or grounding are not realized until the occurrence of a fault in the system. The importance of earthing is only known when an earth fault happens, however the occurrence of a fault may only be a split of a second as the protection system has already cleared out the fault.
Do not let the test comes first, do not let an accident happens before you learn your lesson. Always make sure that in every aspect of electrical design, earthing or grounding is taken into consideration.