I have no idea what category this falls under but "trust and relationships" sounds close enough.
I got a valentine's gift a couple year's back from a guy I didn't like back. I accepted the gift out of courtesy, especially after he noted that he'd travelled to Hong Kong to buy it. He's a sweet guy but I just didn't feel the same way, and now he's moved on and likes someone else. The valentine's gift was a sketchbook I barely used, but I'm still reluctant to throw it away since he knew I'm an artist (hence a sketchbook) so he really put a lot of thought into the gift (left a note on the last page and wrapped it up nicely and everything).
Would it be unethical to toss it out?