I believe this comes from the great Gatsby. A slightly fuller version: …He had a grand vision for his life since he was a boy…. No amount of fire could challenge the fairytale he had stored up in his heart… But I had the uneasy feeling that he was guarding secrets.” So it could be adversity, criticism. They are referring to Gatsby's view (fairy tale) of how his life should be and nothing could put him off.

Context is needed, but "fire" is probably either a metaphor for criticism, or perhaps an allusion to an element of some other genre of storytelling. Again, context is needed.