Even though he was our boss, for the first two hours of each day we only glimpsed Rudy from a distance when he shuffled back and forth from his office to the break room coffee machine. If we called him -- even if we paged him -- he wouldn't answer.

By around 10 a.m. he was a different person. Upbeat. Encouraging. Chatty. Eager to solve job scheduling or materials bottlenecks that could affect our productivity.

Then, by late afternoon he became yet another person. Instead of chatting, he barked orders. Instead of solving actual problems, he yelled about nonexistent ones. Whether we needed his help or not, we did our best to avoid him.

Hold that thought.

It's easy to assume that some people are good leaders and others are not. But the reality is more nuanced. Sometimes you're a great leader. You're empathetic. Insightful. Collaborative. Decisive.

Other times, you're less effective.

Why? According to research, sleep plays a major role in your effectiveness. A 2015 study published in Academy of Management found that bosses who don't get a good night's sleep are less likely to make good decisions the next day. Less likely to foster engagement and collaboration with, and among, their teams the next day.

And are more likely to be abusive (which the researchers define as "hostile verbal and nonverbal behavior") towards their employees the next day.

As the researchers write:

Emerging evidence suggests that leaders might be more (or less) abusive on some days than on others... abusive supervisory behavior varied more within supervisors than it did between supervisors.

Why does sleep deprivation have such an impact on leadership performance? For one thing, tired people tend to make poorer decisions.

But the researchers speculate the real culprit is ego depletion: Since self-control draws on a limited pool of mental resources that can be used up, when your energy is low, so is your self-control. Which means you're less likely to have the inner "oomph" required to be the kind of leader you want to be.

Which makes you less patient. Less tolerant. Less collaborative. More likely to make snap decisions -- and to snap at people, even if your version of "snapping" is only a nonverbal eye roll.

Rudy? He was chronically sleep-deprived. He needed four cups of coffee and a couple hours of quiet time to face the day, and us. But by the afternoon, no amount of coffee -- or "I really want to be a good leader" willpower -- could overcome his fatigue.

The solution, of course, is to always get a good night's sleep.

But like most solutions, that isn't always possible. So what should you do when you haven't gotten a good night's sleep? According to the researchers, don't just try to power through.

Instead, adapt to the fact -- and it is a fact -- that lower levels of physical and mental energy can impact your leadership performance. If you can, put off major decisions. Force yourself to take a beat and think -- instead of just reacting -- before making smaller decisions. 

Recognize that fatigue naturally decreases your tolerance for frustration, and save potentially difficult or confrontational conversations with employees -- if the issue or problem can be put off -- for the next day.

And don't answer emails that require deep thought, or nuance, or fine judgment late at night. Save them for the next morning when you're fresh.

The key is to remember that no one is able, no matter how hard they may try, to always be the exceptional leader they aspire to be -- especially when they're tired.

So do your best to ensure you are at your best.

And when you're not, to adjust accordingly.

Inc