User blog comment:IamJakuhoRaikoben/Chapter 450: Alone in all the World, Review./@comment-4449950-20150831050139/@comment-9595671-20150831153919

Yeah, just cause the anime made it seem like they didn't doesn't mean that Jellal realized what it might lead to and made an excuse right after to stop it.

I think in a way its both the curse due to its contradictory nature, and the fact that after hundreds of years, he's probably dealing with a lot of psychological issues.

Considering his brother died and he wanted to find a way to bring him back to life, then he was cursed to take life but never die himself to stop taking the life of others... eventually he had to snap.

At that moment Mavis' words made him happy, and during the kiss he probably believed even if he couldn't die he'd never be alone again, so the fact a miracle and contradiction killed Mavis right then...

It was basically a Hope Spot, a moment where it seems you have a strong hope towards something... only for that hope to be destroyed causing despair. He essentially had hope, and in an instant that hope died.