I have struggled painfully with the problem of abandoning projects midway. In my case at least, it's not necessary to postulate fancy add-ons like the planning fallacy or the sunk cost fallacy. I think I'm just lazier than I wish I was and simply cannot hold onto a project for very long.

I expect this particular type of failure is more common than a fake cost-benefit analysis which is actually rationalization. I don't even come up with excuses for not finishing what I start. I simply don't finish things, no matter how hard or how publicly I precommit to doing so.

Finishing things is a skill, and from anecdotal evidence I think it goes up with practice. The solution might be to do really, really small things, so that finishing something isn't so difficult for larger things.