I completelly loose my nerve, whenever I'm trying to understand circutry, and a guy says: Ok, We'll just throw a resistor here, capacitator here... And then they shouw a schematic with 30 parts saying: Here is a common use.

@LukeAlmighty add firmware to the mix. Then you're stuck trying to fix someone else's busted circuit with busted ass code.
Bonus round: when the circuit designer starts giving you software design direction because "I know enough to be dangerous" [to my anger management issues].