For years now, doctors have been trying to help us understand that not getting enough sleep has real consequences for the human body, such as weight gain, skin breakouts, increased bouts of illness, and puffy eyes. But the way poor sleep messes with the brain doesn't just result in physical warnings. The evidence of insufficient sleep reveals itself in the way we behave, too.

1. You find yourself arguing or in the middle of conflicts more often.

Sleep deprivation negatively influences mood, making you more prone to issues like depression and increasing your sensitivity to everyday events. What's more, researchers think that a lack of sleep might reduce impulse control. Subsequently, it can be much harder to respond with politeness or think before you say something that gets you in trouble. You might even cut corners or take credit for what someone else does.

2. People keep asking you for clarifications or seem to question your decisions.

Lack of sleep affects the brain's ability to process information and focus well. That, combined with poor emotional regulation, can translate to poor judgment and making decisions without taking a look at data properly. A 2009 study, for instance, found that accuracy in tasks that required quick decision-making was 2.4 percent in sleep deprived people, compared to 4.3 percent in rested individuals. You also might get clarification requests or reactions of surprise simply because you forget to loop important people in.

3. You've become a bit of a klutz.

Great coordination actually requires a decent amount of mental processing, as the brain has to determine exactly where you are in space on the basis of sensory input and send tons of messages through the body to help you stabilize, move, and react. When you're sleepy, though, the brain has trouble keeping up with these demands. Poor focus and attention can make the motor difficulties seem even worse. In fact, a study from A.M. Williamson and Anne-Marie Feyer found that moderate sleep deprivation impairs both cognitive and motor performance at a rate comparable to alcohol intoxication.

4. You're going over material again and again.

Because sleep deprivation affects cognition and focus, it's much harder to make sense of information or to remember it. You might have to ask people to repeat themselves because you unintentionally tune out from fatigue. Note taking becomes obsessive because you don't remember what's not written down, and even then, you need Google Calendar, spell check, and other tools to keep you in line. You might also find that you have to spend more time memorizing points for a presentation, or that you have to read the same paragraph multiple times before any of the content starts to sink in. Another symptom is that you keep going over your finished work to find flaws, feeling like you might have missed something. Any of these habits can translate to a reduced output or lower quality of work.

5. You're spending more to do less.

Lowered impulse control can make it easier for you to overspend in general. But when you are tired, you're also more likely to feel like you don't have the energy or can't be bothered to handle simple jobs on your own. The result? You spend a ton at the cafeteria because you choose not to pack a lunch, or you start looking into services like grocery delivery or housecleaning. You tell yourself your health and time are worth it, but to pay for the services, it's back to work, and you stress yourself out about the bills and subsequently ... don't sleep.

6. You pass on good opportunities.

When you're at your limit physically, the minute someone suggests taking on another responsibility or trying something new for your career, you retreat like a turtle pulls into its shell. You might understand there's a nice chance in front of you, but you convince yourself you're comfortable or don't need it because, subconsciously, you can't stomach the idea of taking on even more.

While we've been pretty conditioned to see burning the midnight oil or getting up before the sun as a prerequisite for exceptional business leadership and success, the reality is, sleep isn't optional. Powering down and actually getting the snooze time your body says is optimal for you is one of the most competitive and intelligent things you can do! Draw the line in the sand and grab your pillow, because in the long run, you're doing yourself a favor.