The Immortal's Lament

"Emperor, you knew the ending all along. Why did you still wager with me?"

"And you? Didn't you see it coming too? Why did you still dare to wager with me?"

"When three walk together, one must be hurt. They are both the people I love most."

"Making others happy at the cost of sacrificing yourself. Is it worth it?"

"I never thought about whether it was worth it. From beginning to end, it was all one-sided on my part."

"Emperor, you lost."

"Yes. I accept my defeat completely."

"If I could start over, I would never become an immortal again."

Premise: How can the past be wiped away with a single stroke?