When heated, coals become incandescent, which means that they glow red-hot. When you're heated up by an argument, chances are you're incandescent with, or characterized by the intense emotion of frustration.
Incandescent, like the word candle, has its origins in the Latin word candere meaning "to glow or shine." Combined with the suffix in meaning "within," its meaning can be easily pulled from the combination of its root words: "to glow or shine from within." Fire crackers are incandescent because they give off brilliant lights when heated, but look up at a blazing fireworks display, and you'll find it's quite moving, or incandescent with intensity and brilliance.
