It sounds like a case of the first 70% of the work taking 50% of the time, and the remaining 30% taking 150% of the time.
My projects invariably seem to take 200% of the time to complete that I estimate, even when I make that time a very big number.
I look forward to seeing your updates in this New Year which I hope will see everyone making good progress on their projects.
It sounds like you have the same problem I do, with getting part way through a project and then realizing how it could have been done better. Then I want to scrap and start over pushing the completion date even farther away. Better becomes the enemy of good enough.
cheers,
Michael