There are numerous books on the subject of the importance of passion as a success driver. Passion as a key component of small business success is a given. Equally important is having a purpose for your small business and your role in it, particularly at the start up stage. Ultimately, without profit both for the business and its owners, passion and purpose will not sustain a small business idea. The lack of profit, by definition, leaves you with an activity you're invested in but not a "business".
At the start up stage Sam's passion centered on his love for doing hands-on things and solving problems. That's what lead him to his current career as a software programmer. Judy's passion also included a problem solving component but involved people not formulas.
Sam and Judy shared a common purpose. Their academic perception of small business ownership as a way to have more time and money to devote to raising a family and doing more of what you love to do.
Profit was least familiar to both of them. They had no business experience to give them an understanding of making money and paying themselves from the proceeds of their business success. Nevertheless, both Sam and Judy figured they could learn about the business side of things as they got started. Passion and purpose along with a cautious enthusiasm is what drove them.