Calm's marketing headline "Calm your mind. Change your life." is a compelling H1 that stands out in an increasingly competitive landscape of meditation and mindfulness apps. Here's why this H1 helps Calm remain at the top of the pack:

• Establishes a clear cause-and-effect relationship between mental calm and life improvement.

• The parallel structure of two short commands creates a memorable rhythm.

• Opens with "Calm" which reinforces the brand name while also stating the primary benefit.

• The periods create deliberate pauses that mirror the mindful breathing the app promotes.

• Progresses from an immediate and achievable action to a significant long-term benefit.

• Balances simplicity with profound impact which helps suggest an accessible transformation.

• Directly addresses the potential user with active verbs that encourage immediate action.

• The brevity of both phrases reflects the simplicity and clarity that meditation provides. Breathe in. Breathe out.

• Avoids meditation jargon which helps in appealing to beginners who may be intimidated at the thought of meditation and starting a new journey.