Michael Schwartz outlines 11 common retirement planning mistakes and provides advice on how to avoid them. The key mistakes include failing to have a proper retirement plan, having improper asset allocation, failing to calculate taxes, and failing to plan for healthcare costs. Schwartz urges readers to evaluate whether they have planned for these issues and offers to discuss how to turn potential mistakes into future strengths. He provides more detail on the first two mistakes of failing to plan and having improper asset allocation, emphasizing the importance of developing a comprehensive retirement plan and properly diversifying investments across different asset classes.