To become happier with an inherited codebase, it's essential to understand what the code does, how it's organized, and its structure. This involves reading available documentation, building a "Hello, World" project that uses the code, and exploring the codebase to identify areas for improvement. Tooling such as static analysis tools, behavioral analysis tools like CodeScene, test coverage tools, mutation testing tools, and profiling tools can help gain insights into the codebase's structure, technical debt, and potential vulnerabilities. By using these tools and understanding how they work, developers can build trust with their team, tackle technical debt, and make changes to improve the codebase.