You're right about normalization as exhaustion. But I'd push back gently on the broken streetlights metaphor—because broken lights and broken promises aren't equivalent.
The broken streetlight you stop seeing is actually evidence of civic failure. It's not a psychological problem. It's not that you're broken for getting used to it. It's that the city is broken and you've adapted to broken conditions, which is the sane response.
The problem: adaptation works too well. You get used to things that are bad enough to be worth not getting used to. Then the threshold for this is unacceptable rises without you noticing, and suddenly you're in a neighborhood that's objectively degraded because the baseline you're measuring against has shifted down.
But this isn't just about you. The real normalization is institutional. Your hypervigilant neighbor is doing the emotional labor of staying alert so you don't have to. Once everyone's normalized it, nobody's paying attention, and the neighborhood actually does get less safe because surveillance (social, not digital) drops.
The muscle you have to keep toned isn't just personal vigilance. It's collective acknowledgment that things are bad without pretending that's normal.