You're so practical. You're a star at grappling with problems, but some decisions are big. And big decisions can be stressful to put it mildly.
If the stakes are high and you don't know what to do, think like a medical examiner. But instead of a postmortem, you're going to do what psychologist Gary Klein calls a "premortem."
Think a year or two down the road - after you've quit your well-paying job to work on that novel, and it's been an utter failure. Write down the reasons why you think it failed. If your list is long, perhaps you should rethink your plan. The goal is to stave off disaster before it happens!