We have all woken in the middle of a dream for some reason and snuggle back, trying to return to your dream. It’s very rare that you are able to return to the dream, well, at least for me.
This is exactly what your editor means when they warn that you can ‘drop your reader out of the story’. In the worst case scenario, your reader may be an acquiring editor who never reads any further. Or it may be a reader who purchased your book who may give it up and never buy another of yours.
What can drop a reader out of your story? Your words may be repetitive,
awkward or klunky, there may be an error of grammar, a plot hole or any of a multitude of other things, some of which may be entirely subjective in the mind of the reader.
What can you do about it? Consider your editor’s comments, polish it to the best of your ability and let it go. Write the best story you can and trust that your reader descends into that fictional daydream.