Combining building and selling skills is key to being unstoppable. Building involves product development, design, and operations, while selling includes marketing, communication, and fundraising. The most successful startup model often has one founder who excels at sales and another who excels at building, like Steve Jobs and Steve Wozniak. However, individuals who can do both, like Elon Musk, have true superpowers and can create entire industries. The giants in any field are those who can build and sell. While it's harder for a salesperson to become a builder later in life, a builder can learn to sell, especially if they have good communication skills. Bill Gates likens it to teaching marketing to an engineer rather than teaching engineering to a marketer. Building skills are more valuable when starting out, but selling scales better over time. Ultimately, it's ideal to possess both skills, but if you had to choose one, starting with building and transitioning to selling is a wise approach.