Darkness is a primal fear of any animal who a) does not sit at the top of the food chain like a hungry Californian sits at the business end of a sushi train; b) is not nocturnal, eyeless, a mole or deep-sea creature.
When the double-As in your LEDs fail, you will be forced to confront that fear.
Ride on? Risking bunyip attack, accidental cross-country sections and the insouciant violence of those big, blind, mole-like creatures, the cars?
Or abandon all hope, dismount, and transform into a humble pedestrian?
BONUS TIP: There are those who do not fear the dark, do not shrink or cower, but use it for their own nefarious purposes - bike ninjas!