There really is no need to go to such extremes, that advice was just a fail safe back when no one knew much about PCs and home electronics.I build mine on carpet too. Well not entirely. I place a section from a large cardboard box on the floor first but that still means I'm kneeling on the carpet. But I always, always wear an antistatic wrist strap when doing a new build. It's possible that something may have gotten static damaged from last time it was built (static damage is often delayed in showing up as a fault) and this build/maintenance just became the push it needed to fall over.
But as long as the PSU is discharged and you ground yourself on a bit of the non painted metal case before touching components, you will be fine. Unlucky for the OP his case is fully painted.
The only part you need to be extra careful with is the CPU itself, which you would normally grab from the sides anyway.