You know what, I've thought about it a little, and I think there's something that's related to my advice and even more important: the most dangerous place for a project is when it feels like it's less than 5% done, and that place is even riskier if it feels like you've spent a lot of time to get it there. If you're soloing a big project your main concern should be motivating yourself to keep going at it, and the best way to do that is doing low effort, high value tasks. The things that you can get done in less than one day that will catapult your project forward, like working on the fundamentals of the gameplay loop, getting some basic levels in so you can start working on the stuff you'll fill the levels with, that type of thing. You shouldn't spend more than one day (unless you're working only like, 1 or 2 hours a day) on any given individual part of the project in the initial stages because it will feel like you're getting nowhere.