Remus lifted his hands in a helpless gestured of surrender. "You DO deserve that. And I know that you care for me, Tonks. Merlin knows I care about you, too." But it came down to the facts. He was old, she was young. And he'd already made a mistake. They would both be waiting for it to happen again, and what did that mean for a relationship?
To Remus, it seemed like that would doom it, if it hadn't been already.
"I love you. You're not mad, or anything close to it. You're young, and you're hopeful. Even in the midst of a war, you're still willing to believe that the best is possible." Remus paused and then admitted. "And I can't convince myself of that at all. I have no prospects. Unlikely as it seems, the baby is the most exciting thing I can picture for my future." Though almost equally terrifying and daunting.
"I want you. But I can't justify continuing as we were." Remus didn't want to lose her. But he didn't want to make another mistake. This was simplest, and in the end, it would be better for her. For him to let go, and simply take as much of a place as a father as possible. "I'll always be there, if you need me. If the baby does. I promise that."