We really are always doing our best. We don't purposly mess up our day or week. Things just happen. We don't always do everything we know to do to achieve the results we want. But, there's not a conscious intention to fail.
We either didn't allow enough time, or we're missing information or we didn't get all the information we neeeded. We often operate on just barely enough information and we get tripped up.
Since most of the time we are doing our best, it's ok that we've failed to achieve the goals we set. The goals were probably to big or not scaled or not thoughtfully resourced.