How to Use the 3weeks App — A Complete Guide from Day 1 to Day 21

If you just installed 3weeks and aren't sure where to start, this guide covers everything from your first challenge to the 21-day finish line.

Step 1: Create a Challenge

Tap the "+" button on the main screen. You'll name your challenge and choose a start date.

Name it specifically. Vague goals are harder to check in against.

"Exercise" → "20 push-ups every day"
"Study" → "10 English vocabulary words"
"Diet" → "No eating after 8pm"

A well-named challenge answers the question "did I do it today?" in two seconds. If you have to think about it, the goal is too vague.

Start today. "I'll start Monday" is the enemy of habit-building. The best time to start is now.

Step 2: Check In Daily

When you've done the thing, tap the check-in button on your challenge card.

After tapping, you can optionally log three things:

Mood — How did it go today? From great to rough. These accumulate into a mood trend graph you can look back on after 21 days.

Completion score — How fully did you hit the goal? If your target was 20 push-ups and you did 12, log 60. Partial credit is still progress.

Photo or video — Attach a workout photo, a picture of your meal, a page of the book you read. After 21 days, you have a visual record of the journey.

All of these are optional. On busy days, just hit the check-in button and move on.

Step 3: Keep the Streak Going

Consecutive check-ins build your streak, shown as "N days in a row" on the challenge card.

Missing a day resets the streak counter to zero — but it doesn't reset the challenge. You just continue the next day. Don't delete the challenge over one missed day.

When you miss a day: don't catastrophize. Research on habit formation consistently shows that one missed day doesn't break the habit — only stopping entirely does. The important thing is coming back the next day.

Step 4: Earn Badges

Hit specific milestones and you'll unlock badges:

7-day Sprout — you survived the first week
21-day Flame — challenge complete
60-day Diamond — two months in
90-day Crown — a genuine long-term habit

The 21-day Flame feels more satisfying than you'd expect. It's a concrete marker of something you actually finished — and it tends to motivate starting the next challenge.

Step 5: Review Your Statistics

After completing 21 days, check the statistics screen:

Calendar view — see which days you checked in at a glance
Weekly pattern — which days of the week you tend to succeed or struggle
Mood trend — whether your mood improves on check-in days
Average completion — how fully you hit your target across the 21 days

This data becomes useful for designing your next challenge. If you consistently struggle on weekends, you can plan ahead for that in the next round.

Common Mistakes

Starting too many challenges at once. Start with one or two. Five simultaneous challenges usually means zero completions.

Setting the bar too high. Your first challenge should be easy enough that missing it would feel embarrassing. "5 minutes of stretching" is a better first challenge than "1-hour workout." You build intensity after you've proven you can show up.

Perfectionism after a missed day. One missed day is not failure. Quitting after one missed day is the only failure. Come back the next day.

3weeks is designed to do one thing well: help you show up every day for 21 days. Everything else — the notes, photos, badges, statistics — supports that single goal. Start small, check in, and see what the flame badge feels like.