For me, it's around product-market-distribution-founder fit. Some questions are:

Product-market: Are folks already spending money on such products or problems? How does my product solve that issue? What are their alternatives, including doing nothing? Are there big players? If yes, there's plenty of money. How's my product different? Any smaller niches that are underserved?

Distribution: How can I reach the target customers? Is that a channel I can actually access? Do i even have a chance to reach them?

Founder: Is that product-market-distribution combination my thing? Is that a distribution channel I want to use, or does it turn me completely off? Do I even want to serve those types of customers?

It might be a super product-market-distribution fit, but if it includes stuff I dislike or even hate, the risk of procrastination, etc., rises sky-high, and everything becomes a pain, a dread, and a constant fight, exhausting my willpower fast and thus causing me to fail.