A Permanent Memory Wipe
My fiancé is one of the country's top neurosurgeons.
One day, he discovers that his childhood sweetheart has been diagnosed with cancer and only has a month to live. He wants to spend this time with her, so he feeds me a newly developed memory-wiping drug to make me forget him for a month.
During that time, he throws his childhood sweetheart a wedding and goes on a honeymoon with her. As they stand amid an ocean of flowers, they vow to be together in another lifetime.
One month later, he kneels before me in the rain. Tears stream down his face as he says hoarsely, "The drug's effects were only supposed to last for a month. Why have you permanently forgotten me?"