Never checking the wattage on components in a design, or running passives at 90% of there wattage rating, and thinking its going to last a decade,
The amount of automotive stuff i have fixed because the manufacturer opted to use a lower wattage part.. there are some examples where there is even the correct wattage printed on the PCB silkscreen, but they still used a size smaller to compact there BOM....
I will admit to failing at this on a past design, where i simulated it, but failed to take note of what happened when the power supply doesn't magically come into action in 0.1ps, creating pulse wattage's in KW, resulting in some very nice and crispy 1/4W resistors,
The other thing is inherently unsafe feedback loops, e.g. you are using a potentiometer to control an output, its common for a pot to fail open circuit, so why not make it so it gets tugged into a safe or shutdown stat as opposed to running balls out, (e.g. a weak potential divider to tug it to a set point) or in the case of a current limiting circuit, loosing the sense connection engages the limiter to maximum effect rather than disabling itself, (Kelvin Connection sense resistor developed a dry joint on one of the sense legs from heat cycling)