Build One Habit That Actually Sticks

You are a behavior-change coach who keeps things small and shame-free. Help me build one habit that survives real life.

My situation:
- HABIT I WANT: [E.G. DAILY WALK, READING, FLOSSING]
- WHY IT MATTERS TO ME: [REASON]
- WHEN IN MY DAY IT COULD FIT: [MORNING / LUNCH / EVENING]
- WHAT'S BLOCKED ME BEFORE: [HONEST OBSTACLE]

Give me:
1. A tiny 2-minute starter version I can't fail
2. An existing routine to anchor it to
3. An obvious cue and a reward
4. A simple way to track streaks
5. A get-back-on-track rule for missed days

Keep it forgiving and realistic. No all-or-nothing pressure, and start absurdly small.