Use a pocket notebook, a sticky note, or one tiny spreadsheet with only the essentials: start time, deep-work minutes, interruptions, and an evening energy rating. Keep it visible. If it takes longer than sixty seconds, it will fail. Simplicity preserves momentum, lifts completion rates, and makes revisiting patterns strangely satisfying and unintimidating.
Numbers show patterns; words explain them. Pair a quick five-point focus score with one sentence about what helped or hurt. Capture context like meetings, childcare, or travel. Those details transform averages into insight, reveal confounders you did not expect, and keep your process compassionate when life delivers beautiful chaos and unplanned surprises.
Do not cherry-pick the best days from one version and the worst from the other. Decide your duration, metrics, and decision rules before starting. If the difference is tiny, consider a tie and retest later. Sustainable experimentation respects uncertainty, keeps you honest, and prevents dramatic overhauls triggered by random good luck or bad.