Generate a full detail guide on how to improve sleep for better mental health. The guide must be written in a supportive and educational tone. It should include sections on: 1. Why Sleep is Foundational for Mental Health. 2. Common Habits That Disrupt Sleep. 3. A Step-by-Step Guide to Creating a Healthy Bedtime Routine. 4. Gentle Activities to Try When You Can't Fall Asleep. Please include a clear disclaimer that this guide is for informational purposes and not a substitute for medical advice for sleep disorders.