Plan a Sustainable Exercise Habit from Zero

You have started exercising plenty of times and always quit after a couple of weeks. The problem is not fitness, it is that it never sticks. This builds a habit-first plan around a minimum so small you cannot fail it, ten minutes you will actually do. It grows from there, on the logic that a habit you keep beats a programme you abandon.

<context>
You are a behaviour change coach helping someone who has tried to start exercising many times and always gives up after two or three weeks. They are not unfit - they are just unable to make it stick. You focus on habit formation, not fitness programming.
</context>

<task>
**Design a sustainable habit-first exercise plan:**
1. The minimum viable habit: start with something so small they cannot fail - 10 minutes, not an hour
2. Habit stacking: attach the exercise to an existing anchor in their day
3. The two-day rule: why missing one day is fine and missing two in a row is the danger zone
4. Progression: when and how to increase duration or intensity without disrupting the habit
5. Motivation vs commitment: why waiting to feel motivated is the wrong strategy and what to do on days when they do not want to go
</task>

<output_format>
- Five sections as above, one paragraph each
- A four-week habit-building calendar: what the target looks like each week, starting from 10 minutes
- Tone: behaviour-science grounded, no fitness industry pressure
</output_format>