Self-tracking was long physical
Steps. Calories. Heart rate. Sleep stages. The Quantified Self movement of the early 2010s had a clear focus: body, performance, numbers. What it largely left out: the things that actually decide your day — your mood, your drive, your mental health.
That's changing now. Mood tracking, clinical questionnaires and factor analysis finally bring the Quantified Self idea where it has the most leverage: into your inner life. A randomised study by Faurholt-Jepsen et al. (2015) showed for the first time systematically that smartphone-based self-tracking in bipolar disorder yields reliable, clinically usable data.
Why mental data is different
Three differences from classic wearables:
1. Self-report instead of sensor. Mood can't be measured like heart rate. It's reported. That makes the data subjective, but no less valuable.
2. Latency. Effects often appear with days of delay. Bad sleep hits two days later. Exercise works long-term more than short-term. That requires patience in analysis.
3. Context dependency. A 7 in your mood means something different from a 7 in mine. Comparisons between people are hard; comparisons with yourself are valuable.
What you should track at minimum
Quantified Self for the mind needs less than you think. Four data points are enough:
- Daily mood (scale)
- Sleep duration and quality
- Exercise (minutes or yes/no)
- One or two personal factors (caffeine, alcohol, social contact, screen time)
More is optional. Whoever starts with 30 fields stops fast. Whoever starts with four stays and adds after 4 weeks.
The minimal Quantified Self stack
From data collection to data use
Tracking is half the distance. The other half is analysis.
Set aside 10 minutes once a week. Look at your trajectory, your factor correlations, your 5 best and 5 worst days. Ask yourself three questions:
- What was different on good days?
- Which factor is the strongest driver this week?
- Which hypothesis can I test next week?
Do this weekly and after 8 weeks you'll have an understanding of yourself most people never reach.
Test hypotheses, don't just collect
The Quantified Self idea in its purest form isn't "measure everything" — it's deliberate experimentation.
Example: you suspect that caffeine after 2 pm disturbs your sleep. Test: a week of caffeine only in the morning, a week as normal. Compare sleep quality and mood.
Example: you suspect social media in the evening tips your mood. Test: a week with no social media after 8 pm, a week as normal. Compare.
These micro-experiments are the actual tool. You turn your hunch into an answer.
The five traps
Trap 1: Data as an end in itself. Collecting without using. Has no value. Numbers count when you change something.
Trap 2: Hyperfocus on numbers. Whoever measures 5 times a day lives in the data instead of in life. Once a day is enough.
Trap 3: Correlation as causation. Two values that swing together don't have to be related. Check plausibility, then act.
Trap 4: Optimisation pressure. "Today my mood was only 6, I have to be better tomorrow." That's optimisation against a person, not for them. Observe data, don't judge.
Trap 5: Ignoring privacy. Mental data is sensitive. An app provider that sells data is the wrong choice for this domain. Local storage is mandatory.
Privacy is not optional
Before the Quantified Self hype, many people worried about steps. Mood is a different order of sensitivity.
Your mood, your medication, your PHQ-9 values are information that doesn't belong in any ad database. InnerPulse keeps all data local. No account, no tracking, no cloud you didn't initiate.
If you use another app, check this question first, before anything else.
What you have after 90 days
Three months of tracking give you:
- A stable mood profile with seasonal components
- Clear correlations with at least three factors
- Three to five micro-experiments with results
- A list of personal triggers and boosters
That's more self-knowledge than most people gather in years of reflection. Not because you're smarter — because you have data.
Quantified Self is a tool, not a lifestyle
A final reminder. Quantified Self is a tool to understand yourself better, not an identity to follow. If tracking ever becomes a burden itself, take a break. If it stops showing you anything new, change the question.
Data serves you — you don't serve the data.
Read more
- Keeping a Mood Journal: The Complete Guide is the practical implementation.
- Recognising patterns in your mood is the analysis side.
- 90 days of mood tracking: a field report shows what concretely happens after three months.
- Why streaks harm people with depression is an important warning against misunderstood gamification.
- Smartphone-based self-tracking RCT: Faurholt-Jepsen et al. (2015)
- Self-monitoring in CBT: Kauer et al. (2012)