Here "Details" especially refers to the points that we thought it is quite tiny to influence the big picture, and then you leave it to a "all right but not perfect" status. It's proved that this habit is as bad as you didn't finish it, especially in Software Development.
Computer system is an tight integrity, you can never figure out which part would never be refered and it is no worth of careness.
It'll save your quite a lot of more time(returning to recover and mend the defect after a period of time costs several times of time) if you make it perfect at any time rather than leave it at the "all right" position. : )