Lust.
Lust was one of the seven death sins. Jet hardly a human being could resist its seductive charms. Who committed such a sin automatically was damned to go to hell.
Love.
Love, one the other hand, was a divine feeling, which only the human race was blessed with. The more you loved, the more it was likely god would open heaven's gate for your soul.
John had already seen both, hell as well as heaven, and he also felt both lust and love, for a certain curl-headed, completely immature, annoying, innocent and sweet someone.
He really didn't know where this would be leading him to.
Sorry, if my English's bad or seams a bit strange. I hope you still enjoyed it.
Faso