Why would he suggest something like that? Shouldn't you start off by grounding yourself in reality, and admitting that life's unending restrictions will simply reel us in whenever we try to dream?
If you start off by talking about all the "shoulds" and "have-tos" and "musts" in your life - if you begin by simply looking at your restrictions, rather than imagining what's possible - you'll limit yourself from the start. By constraining your options, you'll simply guarantee that you'll be doing work that doesn't excite you.
No, the key to finding your passion in work is avoiding any talk of being "realistic." Instead, you need to really let your imagination fly. You need to build a picture of the kinds of things that could draw and keep your attention, and that will only happen if you can let your dreams soar.
Your first clue is the topics that interest you. What fascinates you now? What do you enjoy reading about? What were the kinds of things that really jazzed you as a kid? Do any of those interests still hold your attention now? The "Knowledges" segment of the Flower Course will help you to envision these areas of interest.
Or, here's another way to approach it. Ask yourself this simple question: If I could wave my magic wand, and do anything in the world of work, what would that be? What kind of activities would you do in a given day? What kind of people would you work with, and perhaps even help? What would your working environment look like? What kind of values would anchor you in your work? And so on.
Again, the Flower Course will help you to flesh out each of these areas of interest, and to prioritize them so you know exactly what kind of work would excite you the most. It's only by giving yourself permission to dream that you'll gain a wealth of knowledge about the kinds of work that would make you thrilled to get up in the morning.