In 1981, Severus Snape was hired as Hogwarts' Potionmaster and expressed some regret for the actions that left him under Albus Dumbledore's protection.
"Rash?"
"We had not spoken in seven years," Severus pointed out. "I doubt she would have done the same for my life."
Albus Dumbledore laughed in his face. "My dear boy, can you truly attest that you don't love her just because you tried to throw it out?"
Fifteen classes, fifteen years later, Dumbledore was somehow surprised it was she that summoned his Patronus from his imperturbable, unencroachable mind. Whatever certainty he held she would not take such joy in the memory herself. Not after how long he hated her, not after what happened to her son.
Even Lily Evans couldn't hold a match to the Dark Lord. Such vision could have reshaped the world, and a voice in the back of his head always pointed out that if the boy weren't there to see it, Severus's own students would be. But whatever happened, the days of a magical boy and a magical girl conquering the woods for their games stayed with him.