I've been working on a solo game project for a very long time now, somewhere between one and two years. I took long breaks on occasion (many months at most) but have regularly worked on these projects every week, if not every day (sometimes most of my day).

It feels to me that a huge barrier to making significant work is the ability to play it long, and this is hard for so many reasons.

Long, isolated work forces you to confront your core value. You will have a voice in your head that says, "this is stupid/pointless/bad and it doesn't matter." Other times you'll appreciate the work you're doing as something deep and meaningful to you, an express of who you are right now.

For long, isolated work, you have to find a way to take the first voice less seriously, and turn the volume UP on the latter.