Wow I feel this way on soooo many levels & can totally relate! God I wish I had an answer so I could help you...& myself.

Do do know that in my past, which I hate to reference because we're not our past, but my father was notorious for doing 90% of a job, then leaving it! My mother would get so angry & it would take months or yrs for it to get done.
Did I learn this? Maybe...

I do know if I look deeply, that I start things & don't finish them, especially big & very expensive endeavors bec I think I'm afraid of failure. So I don't finish things then tell myself I didn't fail. Very twisted.
I hate to fail. And I hate to look like a failure. So I stop trying.
It's really pathetic actually. And expensive!