Katy Milkman opens by arguing that effective behavior change requires identifying and addressing the specific underlying obstacle preventing change — impulsivity, forgetfulness, lack of confidence — rather than applying a single generic change strategy regardless of the actual specific barrier involved.

Why this obstacle-specific matching matters:

• Different behavior change obstacles require genuinely different intervention strategies, and applying a mismatched strategy to a given obstacle often fails despite good intentions
• Milkman's extensive behavioral economics research provides evidence-based guidance for matching specific strategies to specific obstacle types
• This opening establishes the book's core diagnostic approach, motivating its subsequent detailed examination of specific obstacles and matched strategies

This opening establishes the book's foundational diagnostic framework, emphasizing obstacle-specific strategy matching as more effective than generic, one-size-fits-all behavior change approaches.