The Sleep You Don't Miss

Late caffeine can wreck your night even when you fall asleep fine. Lingering in your system, it thins your deep sleep — the restorative stage your brain leans on most — leaving rest you may never notice losing.

To find your cutoff, run a simple test: for two weeks, push your last cup earlier by a bit and track how rested you feel each morning. Your body will point you to the right time.