Seven Deadly Sins of Personal Finances Much is written on the “biggest financial mistakes” that people make with helpful tips for avoiding them. We’re used to seeing many common examples of how people can get themselves in trouble through certain activities, such as charging up credit cards, making minimum interest payments, buying cars new rather than used, not shopping auto insurance plans, etc. The list of common mistakes people make in their finances can fill a book, yet they are all rooted in the failure to adhere to the most basic rules of finance. If you follow these rules, you will be less likely to make the common mistakes. If you fail to follow the rules you will be committing one of the seven deadly sins of personal finance and the mistakes will likely follow.