‘Crack’ Your Knuckles
It doesn’t just annoy your friends and co-workers — it may not be very good for you, either. A substance called synovial fluid keeps your joints moving easily. The sound your knuckles make when they “crack” comes when you pop tiny bubbles in that fluid. If you do it all the time, you’re more likely to have swollen hands and a weaker grip over time. It doesn’t seem to raise your chances of arthritis, though.

Bite Your Nails
This can damage your teeth as well as the skin around your nail bed, which can lead to infection. You also may get more colds and other illnesses when you put your fingers, which often carry germs, into your mouth. It can help to keep your nails neatly trimmed or manicured. If stress could be the reason for your habit, you might try things like exercise to manage it. Talk to your doctor if you want help stopping.

Cheat Yourself on Sleep
If you don’t get enough sleep, you’re not just turning yourself into a daytime zombie — you also could be more likely to have high blood pressure, heart disease, diabetes, and depression. And it might be harder for you to learn and remember things. Set a regular sleep routine and stick with it. And do your best to get 7-8 hours a night.

Surf Before Bed
Not waves — the Internet. The “blue light” given off by electronic gadgets like phones, computers, and TVs can mess up your sleep. And some studies show that too much of any kind of nighttime light might be linked to cancer (especially breast and prostate), diabetes, obesity, and heart disease. Calm yourself before bed. If you want to read something, open up a book. Keep your bedroom dark and quiet for better sleep.

Eat Too Quickly
It can leave you less satisfied — and make you more likely to overeat over the course of the day. If you slow down, you could feel fuller with less, because your body has a chance to realize you’ve eaten enough. It can help to focus when you eat: Take small bites, and chew them well.

Skip Flossing
You did a full brush, isn’t that enough? Nope, you need to clean between your teeth, too, if you want to do all you can to get rid of plaque, the sticky bacteria-filled film that causes cavities. Too much plaque also can lead to gum disease, a serious condition that’s linked to other health issues like stroke, heart disease, and diabetes.