None of that accounts for why he should care what would become of him if she's the one to go (he's already got the answer for that one anyway, and of course it's Theresa), but it's still apparently the right thing to say. It's enough to make Sean want to commit to the idea, anyway, for his own sake as much as for hers. It assumes they'll always have that sort of happy end waiting if they stick it out, even if life has done its level best to hammer home the fact that there's no such thing. It's fine, because whether she truly believes it or not, the look in her eyes right now soundly beats everything that's come before. "Okay," he says, just as serious, turning his head subtly toward her hand. "I promise. I'll keep it together. Fer you." It's a change of pace, but if she cares about what happens to him, then he'll have to as well. At least to some degree.