Hindsight is 20/20
Everyone makes mistakes, but it's certainly no fun to do so -- especially in that heart-stopping space of time spent wondering what the repercussions will be.
For example, a networking newbie chooses the wrong RAID array option when working on a SQL server problem -- then spends a tense all-nighter fixing the mess. And still has to face the boss the next morning. But to err is human and it can be enlightening, once you're back on the right track.