What metric replaced top-of-funnel growth as your primary focus once you started charging?

Tracking signups feels great, but churn is the silent killer when real money enters the picture.

Most cancellations aren't caused by missing features—they happen because the product fails to become a daily habit. Changing a user's existing workflow is far harder than building a shiny new feature.

Do seasoned founders ever stop stressing over churn or do they just get better at diagnosing and fixing drop off points early?