The cup hits, the morning sharpens, and for an hour or two you're on. Then by early afternoon, the floor gives out — foggy, flat, reaching for the next cup just to feel normal. By 5 p.m., you're wired and tired at once, and you can't fully sleep on it. Most people blame themselves and drink less, which only makes it worse. The afternoon crash isn't fatigue arriving — it's your morning caffeine leaving, on a schedule, the first sip set. The real cause is the shape of how coffee delivers caffeine: one tall spike, with a cliff on the far side. Here's the curve, drawn — and the flatter one that makes the cliff disappear.