Once again I felt myself frozen by the sense of something irreparable. And I knew that I could not bear the thought of never hearing that laughter any more. For me, it was like a spring of fresh water in the desert. (26.31)
“Fresh water in the desert” is something you can’t do without—something you need to survive; it’s what you dream about in its absence. And all of that value and need sums up what the prince means to the narrator.