Percy Jackson and Athena. Some years after the war, they meet and actually get together. They didn't make sense together, but they made it work, despite everyone else not understanding how they got together or disapproving of the pair. There were also numerous oppositions who wanted Percy for themselves, causing insecurities to grow within the goddess and jealousy to erupt and show her Greek goddess roots.

 

But then she messed up and now he's gone. After succumbing to her issues and starting to be unable to insult and basically emotionally abuse Percy, now she doesn't have a chance to apologize and make it up to him.

 

The next time they meet, he's a stern and serious business man and she's a schoolgirl. Reincarnation and divine punishment dictates. It's a lesson in humility for a goddess, and a lesson in learning to live and love again for a mortal man.