What is the origin of the idiom "the light of one's life" and when to use it?

The idiom "the light of one's life" is a way of expressing deep affection and attachment towards someone or something. The origin of the idiom is not tied to a specific event but is based on the idea of light being associated with positive emotions and warmth. It is used to refer to a person or thing who brings immense joy, happiness, and meaning to someone's existence.