Generate a full, in-depth guide for entrepreneurs on building a 'Second Brain.' The guide must be a practical system for personal knowledge management. It should include detailed sections on: 1. The philosophy behind a second brain: Offloading your memory to reduce mental clutter. 2. A step-by-step guide to implementing the CODE method (Capture, Organize, Distill, Express). 3. A comparison of popular 'second brain' apps like Notion and Obsidian. 4. Practical examples of how to use the system for business strategy, content creation, and project management. Please include a supportive disclaimer.