Framing this in terms of The Beginner's Guide, I think it's more like:

"I just completed a project into which I poured not just all of my time and energy, but also all of my self-worth. It was a massive success. Now I have nowhere to place my self-worth. Doing this again would be both (1) unlikely to succeed, and (2) extremely toxic, just as doing it the first time kind of was. So how do I get out of this mindset without completely destroying myself?"

Amusingly, his response to that question was to make a game about it.

Few people get rewards on that scale (and thus the chance to exit, or at least the time to think about it), but many develop similar relationships to their work (or art). An exploration of the problems in that dynamic (as in The Beginner's Guide) is therefore relevant to a lot of people.