I noticed the same about myself but I still wonder if this isn't just a character weakness. Why exactly can't I be just as careless and free about a project that I'm serious about in the sense of its potential to make money if executed fully? I do think it's a weakness.
Interesting take. I used to think that but looking at psychology, things like the "flow" state or the book "Deep Work" there's something to be said about out enjoyment of something and the motivations for why we do them.
When my motivation to do something is money, even if I find whatever I do interesting, I'm only doing it for money. Looking at it differently, if I wouldn't do what I'm doing if I wasn't being paid for it there the motivation is not the activity itself but the result.
Doesn't "careless" and "serious" are opposite to each other? I find that when I'm working on a project that I'm "serious" about the focus/motivation/purpose is not the project but the result. The "serious about it" is usually something outside of the project.
You know, intrinsic vs extrinsic motivation.
On the other side, I'm right now working really hard to be careless an free about a new project that I'm actually serious about, even as I'm working for it to make money, but the only way that I can accomplish that for myself is by approaching the project as an experiment/adventure and after exploring the worst case scenario realizing that even if I lose $x finite amount, I'm fine with that.
It's quite hard for me tho, maybe you have stronger character than I!