We’ve all had bad nights of sleep and felt drained the next day. For some people, lack of sleep is a lifestyle, one that increases the risk for heart attack, stroke and early death. What you may not realize is how skimping on shuteye can mess us up in the here and now. 

Researchers found that after 17 hours straight being awake, the ability to think, learn and perform tasks requiring skills such as movement, coordination and speed are impaired as much as they would be by a blood alcohol level of 0.05 percent — high enough to be charged with a DUI.

Just as you should never drunk-dial your ex, there are certain things you shouldn't do on lack of sleep. Here are six.

Related: How Much Sleep Do We Really Need?

Don’t: Speak your mind

 Dying to fire off a snarky email to your boss or to the friend who canceled dinner? Or send your spouse to the doghouse for forgetting to walk the dog?

“When you’re sleep deprived, the emotional areas of your brain are over reactive, and the control or executive area of the brain is under reactive,” says Kelly Glazer Baron, PhD, director of the Behavioral Sleep Medicine Program at the Feinberg School of Medicine at Northwestern University in Chicago. The result: You may have a stronger emotional reaction to things that happen to you.

Do this instead: Sleep on it. You may see things differently once you’re well rested. At the very least you’ll be better able to temper your words to be constructive rather than destructive. If it can’t wait, stall yourself by taking some deep breaths. “Think about how to phrase your response or talk to a friend,” advises Baron.

Don’t: Grocery shop or raid the vending machine 

Mayo Clinic researchers found that people who got less sleep — about an hour and 20 minutes’ worth — downed an average of 549 more calories per day than folks who got more sleep.

“Lack of sleep affects the brain’s frontal lobe — which is important for judgment and reasoning,” says Shelby Freedman Harris, PsyD, director of the Behavioral Sleep Medicine Program at the Sleep-Wake Disorders Center at Montefiore Medical Center in the Bronx, New York.

Not only will your brain fail to safeguard your waistline (and health), your body also will nudge you to reach for high-fat, high-sugar foods to try to boost your energy levels.

Do this instead: Try to put off grocery shopping for a day after you’ve gotten a full night’s sleep. While you’re in the store, stock up on healthy snacks so that you’ll at least have them handy next time you’re groggy.

If you’re heading to work after a bad night’s sleep, pack a goodie bag with healthy noshes like fruit, raisins and low-fat Greek yogurt. Reach for these rather than head to the vending machine when you feel a need to eat. If you’re a tea or coffee drinker, go for it in moderation. According to the National Sleep Foundation (NSF), within 15 minutes caffeine can “temporarily make us feel more alert by blocking sleep-inducing chemicals in the brain and increasing adrenaline production.” These effects can last for several hours.

Related: Are You Sleep-Eating WIthout Knowing It?

Don’t: Drive 

Each year, drowsy drivers cause an estimated 5,000 to 6,000 fatal crashes. Being tired affects your ability to concentrate, make decisions and react quickly — all essential skills for safe driving. When you’re sleep deprived, you may even nod off for brief periods while you’re behind the wheel, adds Baron. If you’ve ever been driving and found yourself wondering how you got from point A to point B, it may be that drifted off for a few seconds.

Do this instead: If you have to get somewhere and you can, leave the driving to a family member or friend, join a carpool or take public transportation.

When you find yourself zoning out in the middle of a long road trip, take a break. Ask a passenger (who has a license, of course) to drive for a while. If you’re alone, “get off the road, take a short nap and have some coffee,” advises Baron. The NSF says a 20-minute siesta is enough to reboot, but remember that you’ll feel groggy for 15 minutes or so after you wake up. Be sure to pull over in a safe area (not the side of the road), such as a rest stop.

Don’t: Make an important decision 

“It can be tough to evaluate pros and cons when you aren’t thinking clearly,” says Harris. Also, being tired may skew the way you view a decision. Duke University researchers have reported that sleep-deprived people are more optimistic about decisions they make, especially when it comes to money, and less likely to consider the negative consequences. For example, perhaps you’ve been thinking of switching jobs, but know that you can’t quit your current one until you have another locked in. On a really awful Monday, after a busy weekend and very little sleep, you find yourself ready to quit.

Do this instead: Do everything you can to postpone making a call. Talk to a friend or your spouse before you march into your boss’s office. If you’re on a deadline to make a decision, ask for a few extra days — and then make sure that you catch up on your sleep enough to think clearly. If you can’t put off giving an answer, again it’s a good idea to turn to a trusted friend or even the Internet for guidance.

Don’t: Try to learn something new 

Especially something risky that requires concentration, physical prowess or a steady hand. If you can barely keep your eyes open, it’s possible you won’t be able to focus on what you’re doing. (There’s a reason for the recent push to shorten work hours for medical residents: patient safety.)

If you’re in a cycle of getting inadequate sleep, keep in mind too that even if you do attend a class or other activity where new information is presented if you don’t sleep well the night after you won’t retain much of it. “Sleep is important for the consolidation of new memories,” explains Baron.

Do this instead: Ideally you can reschedule the activity or class. Then make getting enough sleep a priority — especially if you aren’t snoozing because you’re going to bed later than you should based on when you need to get up. If you have to go through with something when you haven’t slept enough and there’s time, take a 20-minute nap.

Related: Block Blue Light and Sleep Better Tonight

Don’t: Multi-task

Even under the best of circumstances, doing too much at once is tough. Switching from one task to another when you’re sleep-deprived ups the likelihood that you’re going to make a mistake. The frontal lobe of the brain isn’t as active when you’re pooped: Do not chop onions while helping your kid with his math. Put down the sharp knife until the child can calculate the perimeter of a circle on his own.

Do this instead: one thing at a time. In fact, research shows there’s no such thing as multitasking. What may look like accomplishing several things at once is really a rapid-fire switch from one task to another. Start with whichever activity is a priority, complete that and then move on. Even if you’re as rested as Sleeping Beauty, you’ll be better off: It can take twice as long to accomplish something when you’re trying to multitask, experts say.  

Catherine Winters is a freelance writer who specializes in health.