The unexpected gift was a goodbye.

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I debated over whether to flip “goodbye” and “gift.” I decided I liked it better this way, as it puts the motives and emotions of the person leaving more into focus for me. The person leaving is the one who defined the parting as a gift. But when you flip the two words, the focus moves onto the recipient. The recipient is the one who defines the characterization of the goodbye.
Language is weird.