We live in a time when your 20s are basically a protracted adolescence, making it acceptable to spend that decade in complete squalor. By the time you turn 30, though, there are certain teenage-level habits that you really should've grown out of. These are some of them.
Not brushing your teeth before bed
You've known that brushing your teeth before bed is a thing you should have been doing since, oh, early childhood. But without mom or dad around to nag you, it may be a good habit you let go by the wayside somewhere along the way to adulthood. You really gotta pick that habit back up, even if only for vanity's sake -- as you age, your teeth will begin to yellow and develop ugly staining, especially if you're a regular coffee or tea drinker, or if you never managed to quit smoking. If an appeal to your vanity doesn't move you, how about an appeal to your wallet? Dental work is crazy expensive, even if you have good insurance.
Leaving your fingernails and toenails unattended
Your finger- and toenails should be three things: clipped, clean, and free of fungal infections. Use a clipper to keep your nails at a reasonable length -- clipping after you've showered, when nails are softer and easier to work with, can make that process a bit less of a production. A nail brush or orange stick can be used to remove dirt and grime from under nails. If you have a problem with fungus developing under the nail, use an over-the-counter treatment like Fungi-Nail; if problems persist, see a doctor.
Picking at your face
It's satisfying, to be sure, but picking at your face will make you look terrible. Stop doing that! You've lived with blemishes for long enough now to know that picking at them will only make things worse, so why are you still marring your face by digging at blackheads or popping pimples? Slap some benzoyl peroxide on that zit and be done with it.
Having a filthy keyboard and/or cellphone
By now, you're probably aware that your keyboard and cellphone are really, really germy. Here's the thing: cleaning them is as simple as wiping them with a cotton ball dipped in rubbing alcohol, or using a pre-moistened tech wipe. So there's not really much of an excuse not to keep things like cellphones, tablets, and laptops -- for which you've likely paid a pretty penny -- clean and streak-free.
Not washing your sheets and towels regularly
Here are the guidelines: sheets should be changed and laundered every one to two weeks. Towels should be washed after about three uses. Those are guidelines, so there's some flexibility, but if you're only changing your sheets twice a year or using a towel for a month straight, you've got some laundry to do -- and some better habits to adopt.
Not making the bed
Grown-ups make their beds. There, I said it. Nothing screams "petulant teenager" quite like a room in which the bed linens are strewn about. The thing is, making the bed takes a minute or two, tops, and that minimal amount of effort will make such a big difference in the appearance of your bedroom. While you're at it, pick the dirty underpants up from the floor and put them in the laundry hamper.
Leaving food that's gone bad in the fridge
Look, at some point you're going to have to open that refrigerator door. And the situation inside is definitely not going to get better with time, so put your big-boy pants on, hold your nose if you must, and remove whatever it is that's causing you such stress. Then remember how bad it was, and vow to be diligent about not allowing rotting food to linger.
Not attending to the trash
Taking out the trash is a fairly mindless and effort-free household chore, which is why you have no excuse for those tissues that are toppling from the wastebasket onto the bathroom floor, or for a kitchen garbage can overflowing with grounds-filled coffee filters and egg shells. Better yet, kill two birds with one stone and open the fridge to check for spoiled food right before you take out the trash!
Having bad table manners
Talking with your mouth full. Wiping your greasy hands on your shirt rather than using a napkin. Reaching across other diners to grab the salt and pepper shakers. Those are all actions that relay to the rest of the world that you have bad table manners, and by the time you hit your 30s, you should be able to do better than that.
Not wearing clean underwear and socks every day (this means no holes!)
There's nothing quite like the excruciating embarrassment of turning up at someone's home, being asked to remove your shoes, and realizing that your socks stink and are full of holes. A good way to prevent that is to act like the responsible adult you are and wear a fresh, hole-free pair of socks every day. Fortunately, you're less likely to be asked to remove your pants while visiting a friend's home (or maybe you are likely to be asked to remove your pants, in which case, I'd like to get to know your friends better!) Still, though, the same holds for underwear -- clean and intact is what you want to aim for, every single day.