A task left undone remains undone in two places: at the actual location of the task, and inside your head.
Incomplete tasks in your head consume the energy of your attention as they gnaw at your conscience. They siphon off a little more of your personal power every time you delay.
No need to be a perfectionist, that's debilitating in an imperfect world, but it ís good to be a "completionist". If you start it, finish it - or forget it.