[rw140]

My current rule of thumb is that if I don't think that I'm 90% done when I'm only 50% of the way through my schedule I'm going to miss my deadline.

My suspicion about the cause of this is that I'm conflating 'easy' with 'doesn't take long'. I think there may be some other factors to do with not wanting to admit I'll break stuff when tidying code (so not allowing time to fix it) and somehow assuming that all the little niggles that only take a couple of hours to fix will all be fixed in the same couple of hours.