Sleep happens in roughly 90-minute cycles that move through light, deep and REM stages, and waking up mid-cycle is often why a full night's sleep can still feel rough.
Rather than chasing an exact number of hours, try counting in 90-minute blocks and giving yourself a consistent wind-down window before bed.
Small, boring habits — a fixed wake time, dimmer light in the evening — move the needle far more than any single sleep gadget.
