1. When you're 21, you're not actually a grown-up—you're a baby. You can't see this at 21. At 21, you're all, "I will forever be SO OLD at every age after this one." When you near or enter your 30s and have experience working in offices and interacting with actual grown-ups who are not your parents, you realize that people actually think 27-year-olds are children and 21-year-olds are basically fetuses.
2. It's important you treat your body well because it does, in fact, age. When you near 30, you will start to see a difference in how your friends who spent their teens and 20s on drunken, drugged-out benders look versus your friends who never drank that much and always wear sunscreen. You now wear sunscreen every day, even on cloudy days.
3. Hangovers actually totally suck and are not worth it. It really is true that they get worse as you get older. Once you accept this as your truth, you drink less at social gatherings and, on the ~upside~, can function like a human being the next morning. Like, Pilates-class-before-work function.
4. You can go out with friends and not drink without feeling you're doing something wrong or weird. Drinking is your choice and you don't have to take shots at da club on a Wednesday just because your roommate is telling you to. Your roommate is the kind of person who, at the end of a long night, barfs in her trashcan.
5. Aging isn't actually bad. Partly because a wrinkle here and there can make you look distinguished and partly because as you get older, you become more comfortable with yourself and embrace your perceived flaws rather than wanting desperately for them to be different.
6. Getting your heart broken is good. Because you always end up with someone better, and going through that kind of emotional trauma makes you a stronger, wiser, more interesting woman.
7. Guys who treat you like shit won't change. You're better off leaving them right away than hoping for them to be any different than the assholes they are. Besides, he probably sleeps on a mattress on the floor.
8. Worrying about other people who you think are "better" than you in some way gets you nowhere. The only person worth worrying about is yourself. If you care so much about what other people are doing, something isn't right with your own life.
9. Call your parents more than you think you should. Everyone has friends who lose parents too soon. Not one of them every dreamed they would be that unlucky person in their friend group.
10. The things you worried about in your early 20s were so silly. Like, straightening your naturally not-straight hair every day, always getting bikini waxes, counting every single calorie you consume—the list is endless.
11. Seriously, it doesn't matter if you gain or lose five pounds! Obsessive monitoring of your weight tells you nothing about your health or attractiveness, and no one who looks at you on a regular basis cares or even notices.
12. Life is full of really great phases and really shitty phases. It sounds cliché but it's true: Every time something really, really bad happens to you, you know that things can only get better (and they usually do).
13. You shouldn't be afraid to ask for time off work. You have vacation days so you...take vacation. If your boss is sane and reasonable, she will never get mad at you for going to the doctor during work when you need to or taking a week off to spend with your family on a beach somewhere. If she is not sane and gets mad about that stuff, then it's time to quit because life is too short to work for haters. YOLO is real.
14. Saving money was the smartest decision you ever made. Or if you didn't, one of your worst regrets. When you're 28 and have a growing bundle of money in your bank account and a nice nest egg for a future real estate purchase, and realize over dinner that your friend doesn't even have a retirement account because she spent all her money on designer purses, you are so glad you listened to your mom when she told you to start saving as soon as you started working.
15. You're better off with a smaller group of good friends than a bigger group of shitty friends. As you get older, you realize the toxic people in your life managed to fade away—because you stopped putting up with their flakiness, because you stopped partying too hard on weeknights, because you started refusing to hang out with people who don't make you feel good. And life is so much easier.
16. If it makes you feel uncomfortable, you don't buy it. You don't fool yourself into thinking you'll be able to break in a really uncomfortable pair of heels or fit into a too-small dress after you lose seven vanity pounds. You only buy and wear things that make you feel fly just as you are.
17. You will fail a lot before you succeed. Failing doesn't mean you will never or cannot succeed—it just means you haven't succeeded yet.
18. FOMO is fake. So your friends all went to Miguel's party without you and drank his cRaZy*~ punch and won't shut up about how they were so drunk they did [X dumb thing that is not as funny as they think it is, dear god] at brunch on Saturday? I'm so bored just writing that sentence. And you are not missing out on anything.
19. You realize that this saying is true: In your teens, you care what everyone thinks about you; in your 20s, you don't care what they think about you; and in your 30s, you realize they weren't thinking about you at all.
This article originally appeared on Cosmopolitan.com. Minor edits have been made by the Cosmo.ph editors.