Say your plan is to read a book in one week.
On the first two days, you read furiously and make good progress. On the third and the fourth day, you are unable to read much because you are too busy at work. On the fifth day, one idea you read makes you put the book down and think. When the week is over, you have read 60% of the book’s pages.
Seen one way, your plan was a failure. You couldn’t meet your target. On the other hand, 60% is great progress. Without this plan, you likely would not have gotten that much reading done.
Plans are made not just for getting done. They are also made for getting started, to discover the unknown unknowns and to keep us moving.