Chronic stress enters habit systems by shifting the brain away from deliberate, goal-directed behaviour toward whatever is already installed, before a single conscious choice is made. The conditions that habits depend on, time, space, cognitive capacity, and a coherent sense of self, are precisely what sustained stress weight erodes first, and it does so the way mould does: quiet, patient, and already through the wall by the time you notice the smell. This bundle maps that erosion, names what is driving it in the specific conditions of 2026, and builds the framework for designing around it rather than through it.