Most people log too little or too much. Too little: a mood emoji and a sleep number from a ring. Too much: 40 custom habits, none of them comparable, none of them timestamped.

Correlation needs a taxonomy. Same fields, same units, enough days. Here is the minimum set we use in Habisty—and you can run it on paper if you want. The app exists so you do not have to.

This is not medical advice. It is a logging protocol.

Sleep: duration is not the whole story

Log time in bed, estimated sleep, and a quality rating you report in the morning—not only a wearable score. Apple Health (optional with Pro) can fill in some sleep and step data. Keep the subjective rating too; a mismatch is a prompt to look for context, not a diagnosis.

Add one tag when the night was not a default night: late caffeine, alcohol, travel, illness, screen-until-sleep. Without the tag, an 85 and a crash look like a paradox. With the tag, they look like a mechanism. We wrote the full version of that paradox in High Sleep Score, Low Energy.

Stimulants: what, how much, when

“Had coffee” is not a field. Log:

Type — coffee, tea, pre-workout, nicotine, whatever you actually use.
Dose you can repeat — cups are messy; pick a unit and stick to it.
Clock time — this is the field people skip and the one that explains afternoon crashes.

Caffeine can affect sleep hours after it is consumed, but the effect and a sensible cutoff differ by person and dose. If afternoon energy is the question, log last-dose time before adding another supplement. See How to Find a Caffeine Cutoff That Works for You.

Focus: blocks, not “was productive”

A day is not binary. Log start, duration, and a quality 1–10 for the blocks you care about (deep work, training, creative). Skip the hours you were in Slack. Those are not the experiment.

Over a few weeks you want to ask: which sleep + stimulant + tag combinations sit under your best blocks? That question is impossible if “focus” is a single checkbox.

Journal tags: the interpreter

Numeric streams do not capture every change in a day. Add a short tag set and reuse it: travel, high social, deadline, sick, rest day. Free text can add context, but reusable tags are easier to compare over time.

How much is enough

Four to six weeks of reasonably consistent logs can be more useful than a long record that lacks context. Daily completeness matters more than perfect precision. If you miss a day, leave it missing rather than entering a made-up completion.

Habisty’s logging layer is this taxonomy: comparable fields, not a guilt calendar. NEXUS only gets interesting after the fields exist. For a balanced view of streaks and context, read When Habit Streaks Help—and When to Track More Context. For the category shift, Habit Tracker vs Life OS.

If you want the fields already structured—and an AI layer that can help you review them—join the waitlist.