Eric was always in a constant state of mourning. The grief never seemed to lift from his shoulders, he had only gotten good at pushing it deep down inside and tucking it away for later. But, like a slow acting poison it filled him and would never stop coursing its way through his veins. It was like air, he needed it on some level. Perhaps to prove to himself that he could still feel something. At least that was one thing he knew he was unfaulteringly good at, suffering. Mourning. Grieving.
Leeloo was worth that pain. He would have mourned her for all of eternity had she not reappeared in this life and when she left it again he would return to that feeling and embrace it. He owed her that much.
Eric offered Leeloo a warm smile and squeezed her hand gently, "You grieve for the loss of the people you love when they're gone. Even if they did serve their purpose. No one ever wants to lose the person they love, not for anything in the world. Your presence makes such an impact that having to deal with that loss from the world is far greater. I guess it's kind of a petty thing, selfish, but I don't care. I would rather have you here and fight beside you against all of the evil in the world than lose you to save humanity." He loved her but not in the same way that Peter did, and Eric wasn't sure if she knew even that much. He couldn't recall telling her before how he truly felt about her, what impact she had on his existence. You never got over someone like Leeloo and he never tried to. He and Peter just managed to go in without her there.