A light can run out of fuel or electricity or the fuel can be cut off. You can break a light so that it no longer works. Light can be obscured as by a fog.

Yet, darkness never extinguishes light as long as the light is burning. Indeed light always extinguishes at least some part of darkness.

For these dark days of December 2023:

“If I say, ‘Surely the darkness shall cover me, and the light around me become night,’ even the darkness is not dark to you; the night is as bright as the day, for darkness is as light to you.”
Psalm 139:11-12 (NRSV):