Many people end relationships to prevent being left behind. Our desire for security can prompt us to preemptively strike against an uncertain threat, even if in doing so we also hurt ourselves. The usual explanation is that preemptive behavior comes from fear. A new study shows that lack of hope is a more robust and persistent predictor of defensive aggression. The conclusion that couples can strengthen their relationship by instilling hope in one another about the future. “We sometimes forget to do those things, to say we’re a team, we’re committed, we have a shared vision for the future.”