If you have reached the age of 25, I have a bit of bad news for you, to wit: it is time, if you have not already done so, for you to emerge from your cocoon of post-adolescent dithering and self-absorption and join the rest of us in the world. Past the quarter-century mark, you see, certain actions, attitudes, and behaviors will simply no longer do, and while it might seem unpleasant to feign a maturity and solicitousness towards others that you may not genuinely feel, it is not only appreciated by others but necessary for your continued survival. Continuing to insist past that point that good manners, thoughtfulness, and grooming oppress you in some way is inappropriate and irritating.

Grow up.

And when I instruct you to grow up, I do not mean that you must read up on mortgage rates, put aside candy necklaces, or desist from substituting the word "poo" for crucial syllables of movie titles. Silliness is not only still permitted but actively encouraged. You must, however, stop viewing carelessness, tardiness, helplessness, or any other quality better suited to a child as either charming or somehow beyond your control. A certain grace period for the development of basic consideration and self-sufficiency is assumed, but once you have turned 25, the grace period is over, and starring in a film in your head in which you walk the earth alone is no longer considered a valid lifestyle choice, but rather grounds for exclusion from social occasions.

And now, for those of you who might have misplaced them, marching orders for everyone born before 1980.

1. Remember to write thank-you notes. If you do not know when a thank-you note is appropriate, consult an etiquette book — the older and more hidebound the book, the better. When in doubt, write one anyway; better to err on the side of formality. An email is not sufficient thanks for a physical gift. Purchase stationery and stamps, set aside five minutes, and express your gratitude in writing. Failure to do so implies that you don't care. This implication is a memorable one. Enough said.

2. Do not invite yourself to stay with friends when you travel anymore. Presumably you have a job, and the means to procure yourself a hotel. If so, do so. If not, stay home. Mentioning that you plan a visit to another city may lead to an invitation to stay with a friend or family member, which you may of course accept; assuming that "it's cool if you crash" is not. Wait for the invitation; if it is not forthcoming, this is what we call "a hint," and you should take it and make other arrangements.

3. Do not expect friends to help you move anymore. You may ask for help; you may not expect it, particularly if your move date is on a weekday. Your friends have jobs to go to, and you have accumulated a lot of heavy books by this point in your life. Hire a mover. If you cannot afford a mover, sell your books or put them in storage — or don't move, but one way or another, you will have to cope.

4. Develop a physical awareness of your surroundings. As children, we live in our own heads, bonking into things, gnawing on twigs, emitting random squawks because we don't know how to talk yet. Then, we enter nursery school. You, having graduated college or reached a similar age to that of the college graduate, need to learn to sense others and get out of their way. Walk single file. Don't blather loudly in public spaces. Give up your seat to those with disabilities or who are struggling with small children. Take your headphones off while interacting with clerks and passersby. Do not walk along and then stop suddenly. It is not just you on the street; account for that fact.

5. Be on time. The occasional public-transit snafu is forgivable, but consistent lateness is rude, annoying, and self-centered. If we didn't care when you showed up, we'd have said "any old time"; if we said seven, get there at seven or within fifteen minutes. Do not ditz that you "lost track of time" as though time somehow slipped its leash and ran into traffic. It shows a basic lack of respect for others; flakiness is not cute anymore, primarily because it never was. Buy a watch, wind it up, and wear it everywhere you go.

6. Have enough money. I do not mean "give up your scholarly dreams and join the world of corporate finance in order to keep up with the Joneses." I mean that you should not become that girl or boy who is always a few dollars short, can only cover exactly his or her meal but no tip, or "forgot" to go to the ATM. Go to the ATM first, don't order things you can't afford, and…

7. Know how to calculate the tip. Ten percent of the total; double it; done. You did not have to major in math to know how this works. You are not dumb, but your Barbie-math-is-hard flailing is agonizing and has outstayed its welcome. Ten percent times two. Learn it.

8. Do not share the crazy dream you had last night with anyone but your mental wellness professional. Nobody cares. People who starred in the dream may care, but confine your synopsis to ten words or fewer.

9. Learn to walk in heels. Gentlemen, you are at your leisure. Ladies: If you wear heels, know how to operate them. Clomping along and placing your foot down flat with each step gives the appearance of a ten-year-old playing dress-up, but a pair of heels is like a bicycle — you need momentum to stay up. Come down on the heel and carry forward through the toe, using your regular stride. If you feel wobbly, keep practicing, or get a pair that's better suited to your style of walking. It isn't a once-a-year prom thing anymore for a lot of you, so please learn to walk in them.

10. Have at least one good dress-up outfit. A dress code, or suggested attire on an invitation, is not an instrument of The Man. Own one nice dress, or one reasonable suit, or one sharp pair of pants and chic sweater — something you can clean up nice in for a wedding or a semi-formal dinner. You don't have to like it, but if the invitation requests it, put it on. Every night can't be poker night. Which reminds me…

11. Do as invitations ask you. Don't bring a guest when no such courtesy is extended. Don't blow off an RSVP; it means "please respond," and you should. "Regrets only" means you only answer if you can't come. If the party starts at eight, show up at eight — not at seven-thirty so you can go a "better" party later, not at eleven when dinner is cold. Eight. Cocktail parties allow for leeway, of course, but pay attention and read instructions; your host furnished the details for a reason.

12. Know how. Know how to drive. Know how to read a map. Know how to get around. Know how to change a tire, or whom to call if you can't manage it, or how to get to a phone if you don't have a cell phone. We will happily bail you out, until it becomes apparent that it's what you always need. The possibility of a fingernail breaking or a hairstyle becoming compromised is not grounds for purposeful helplessness.

13. Don't use your friends. It's soulless. It's also obvious. If the only reason you continue to associate with a person is to borrow his or her car, might I remind you that you have now turned 25 and may rent your own.

14. Have something to talk about besides college or your job. College is over. The war stories have their amusements, but not over and over and not at every gathering. Get a library card, go to the movies, participate in the world. Working is not living. Be interested so that you can be interesting.

15. Give and receive favors graciously. If you have agreed to do a favor, you may not 1) remind the favoree ceaselessly about how great a pain it is for you, or 2) half-ass it because the favoree "owes you." It is a favor; it is not required, and if you cannot do it, say so. If you can do it, pretend that nobody is watching, do it as best you can, and let that be the end of it. Conversely, if you ask for a favor and the askee cannot do it, do not get snappish. You can manage.

16. Drinking until you throw up is no longer properly a point of pride. It happens to the best of us, but be properly ashamed the next day; work on your tolerance, or eat something first, but amateur hour ended several years hence.

17. Have a real trash receptacle, real Kleenex, and, if you smoke, a real ashtray. No loose bags on the floor; no using a roll of toilet paper; no plates or empty soda cans. You are not a fierce warrior nomad of the Fratty Bubelatty tribe. Buy a wastebasket and grown-up paper products.

18. Universal quiet hours do in fact apply to you. They are, generally, as follows — midnight to six AM on weekdays, 2 AM to 8 AM on weekends. Mine is a fairly generous interpretation, by the by, so bass practice should conclude, not start, at ten PM. Understand also that just because nobody has complained directly to you does not mean that a complaint is not justified, or pending. Further, get your speakers off the floor. Yes, "now." Yes, a rug is still "the floor."

19. Take care of yourself. If you are sick, visit a doctor. If you are sad, visit a shrink or talk to a friend. If you are unhappy in love, break up. If you are fed up with how you look, buy a new shirt or stop eating cheese. If you have a problem, try to fix it. Many problems are knotty and need a lot of talking through, or time to resolve, but after a few months of all complaining and no fixing, those around you will begin to wonder if you don't enjoy the problems for the attention they bring you. Venting is fine; inertia coupled with pouting is not. Bored? Read a magazine. Mad at someone? Say so — to them. Change is hard; that's too bad. Effort counts. Make one. Your mommy's shift is over.

20. Rudeness is not a signifier of your importance. Rudeness is a signifier of itself, nothing more. We all have bad days; yours is not weightier than anyone else's, comparatively, and does not excuse displays of poor breeding. Be civil or be elsewhere.