Technical Debt.
It's usually thought of as being a programming thing, but it applies to creative endeavors too.
Decisions you make early on in the creative process result in tiny little interests over a period of time that would eventually take more of your time and effort to correct or continue that it just isn't economical with your hours in the day any more.
I actually have an example of this at the go: Let's say you start a generic fic in a space you enjoy writing in. Something quick and easy. Without thinking too hard about it, you throw up 10, 20, hell maybe even 40 chapters. What started as a quick test of your writing ability just for fun has spiraled into something you feel an ethereal need to actually care about and put real planning and effort into. Decisions you made at the start of the fic start coming back to haunt you, writing decisions you made in the spur of the moment with no planning attached are bottlenecking not only your writing ability, but the far more important factor: Time. It takes you 2, 3, 4, 5 times as long to push out a chapter now, and you still won't be as satisfied with the result as when this was a simply test of your own skill, now it has to BE something, at least in your own mind. You've accrued enough technical debt that fixing it isn't possible without starting over, continuing it isn't economical, and there is no logical fallacy left to justify continuing.