I'll sit down to put the finishing touches on a song. The drums are always tricky to EQ (http://en.wikipedia.org/wiki/Parametric_equalizer), especially the snare. I'll easily spend 20 minutes carefully dialing in the exact sound I'm looking for. Sometimes I'll spend over 5 minutes on a single frequency band, agonizing over the effect of a single decibel boost or cut. Finally, after I've gotten it to sound perfect, I realize that the frigging bypass button is on. In other words, the equalizer wasn't even on. I was completely imagining the changes, yet for 20 minutes I was certain that my delicate adjustments were really doing something.
I'd be embarrased about it, but it's happened to nearly every recording engineer. IMHO the placebo effect applies more strongly to sound than any other sense.
tl;dr: Audio nerds sit around in darkened rooms by themselves uselessly twiddling their knobs for hours on end.