Kudos. I having the same problem. I guess its when you know just enough about the market, your product, and your goals.

• What are our business goals, success metrics, and vision?
• Who are the users we want to target and their needs we are trying to fulfill?
• Who are our direct and indirect competitors and their strengths and weaknesses? - How are different from the current market?
• What core features that will make this product work? Do these features meet the goals for of company? Users? & separate us from the competition?
• How do other people solved these problems?
• What are our key assumptions going into this?