When an otherwise solid employee consistently struggles in one performance area, it's easy to view them almost solely through the perspective of that weakness.

When an employee makes a mistake—especially a major mistake—it's easy to forever view them through the perspective of that mistake.

I know, because I've done it.

Years ago I worked in a book manufacturing plant and a tech accidentally left a small piece of tape on the film before the plates were exposed. As a result, two words were missing in hundreds of thousands of books. The resulting repairs cost over $100,000.

(I know what you're thinking: "Two words? Two words missing in an 800-page book? Couldn't you have just let it go?"

I have two words for you: Um, no.)

In every other regard he was a great employee, and had been for years. Still, whenever I saw him I thought about that mistake.  I know it affected the way I viewed him, and I can't say it didn't affect how I treated him.

I like to think it didn't. But if I'm honest I can't be certain.

How I viewed him—and how I'm sure many other people viewed him—was unfair. Like every other employee he was a sum of his parts. He made a major mistake, but he was also one of the hardest-working and most productive employees in the facility.

Did one error forever tarnish his record? Did one mistake make him a sub-par employee?

Those are tough questions to answer, ones that can be argued intelligently from either point of view.

His error cost more than our spoilage budget for the entire year. It also created a major issue with one of our biggest customers, partly because the delays caused by re-work almost impacted getting books to bookstores on time, but also because the author (one of the top three bestselling authors of the decade) heard about the mistake and threatened to move to another publisher.

At the same time, it was just one error in a job where the potential for mistakes was extremely high. Plus the same error, under different circumstances, would have been a lot less expensive to correct. And it's possible that if we hadn't caught it, no one would have. (Is there a foul if there is no harm?)

So did one mistake, however major, turn a previously outstanding employee into a poor performer whose work should always be in question? I don't know.

What I do know is when I looked at that employee through the perspective of that one mistake, I missed the rest of him.

If you look at your employees through just one performance perspective, you miss the rest of them—and you mismanage the rest of them, too.

Did his mistake make him an overall outstanding employee with one blemish on a superb record? Yes.

Did it forever make him an employee that should not be considered for promotions and other opportunities? I don't think so.

You might disagree.

But what it did make him is human: Just like me, just like you, just like your employees.

Employees are, first and foremost, people. Do your best to always treat them that way, even—in fact, especially—when things go terribly wrong.

One mistake or one performance weakness is just one part of the whole person. Step back and think about the whole, not the part.

In the right circumstances, forgiveness could be the most powerful leadership tool you possess.