This is exactly it! The triple whammy of the work getting harder, expectations getting higher, and coping with potential failure once you call it "done".
When the end is in sight how close to completion you are isn't useful as ego plays a bigger part and so needs to be factored in. Percentage completion becomes a non-useful metric as it doesn't help you get to you objective of completion, if anything it's harmful as I tend to beat self up for lack of progress. As to what that metric is useful at the end point I don't know. But closeness to completion doesn't help me finish.
I use ego as a substitute but some human factor needs to be accounted for.