expression
cannot live without; means the world to one
Fixed expression meaning someone or something is so important that one cannot bear even a moment without them. Often used in romantic or deeply affectionate contexts.
彼女は私にとって夜も日も明けない存在だ。
She means the world to me; I can't live without her.
この子は私にとって夜
This child is so precious to me that I can't imagine life without them.