Ellie, I have to disagree with you cannot sell products through affiliate marketing that you're passionate about. I am doing exactly this. In fact, I use the products myself and my whole family does. It all comes down to finding something you're passionate about and finding a company that has an affiliate program.
As to finding your passion. It is usually hiding in plain sight and once you find it, you go "but I knew that already". At least that was the case for me