The last two sentences of The Box of Delights by John Masefield.

‘Have you had a nice dream?’

‘Yes,’ he said, ‘I have.’

Why? John Masefield, why did you do it? I’d followed Kay Harker through 308 pages of adventures, from mysterious strangers, who apparently remembered this land from pagan times, warning him that ‘the Wolves are running’, through trips in time, changes in size, encounters with talking animals and medieval philosophers, flying cars, pompous policemen – and I’d even read the poems you’d stuck in the text, word for word, and how many readers do that and don’t just skip the poems and carry on with the story, and then, and then, you go and spoil everything.

It was all just a dream.

Is there any more pathetic, more deal breaking, more deceitful and fraudulent phrase in the whole of literature? I, as the reader, have accompanied the writer through the story, accepting it and embracing it, and then, at the end, the writer turns around and spits in your eye: Ha! Fooled you! It was all a dream.
Is there ever any good reason for using this trope? There wasn’t in The Box of Delights. The story was finished, Masefield didn’t need the device to dig himself out of a plot that had spun out of control. Tolkien, in On Fairy Stories, is quite right: any tale that uses this device automatically disqualifies itself from consideration as a fairy tale, indeed, as a good story in the first place, the framing device inevitably disfiguring the narrative beyond repair.

So, writers, however vivid your own dreams, however deep the situation you’ve created for your characters, don’t do it! Never, ever, ever end your story with a dream.