Girls, here are 17 things you must know before you turn 21...

1. Work a service industry job.

You'll grit your teeth when customers make ridiculous demands, show up ten minutes before closing, or ruin a display you carefully put together, but work builds character and working a service job means you'll never be the kind of awful customer who makes employees cringe.

2. Go on dates with different people.

In order to know what you want from someone else, you need a basis for comparison, which means dating different people! Keep this in mind: you want to wind up with someone who makes you feel like the best version of yourself.

3. Travel as often as you possibly can.

Someday you'll have obligations that will make it hard to pack a suitcase and disappear somewhere foreign and exciting. Enjoy wanderlust while you have ample time and the ability to!

4. Keep a journal.

I cannot tell you how many times I trip over an old photo or note that reminds me of something from my past I'd completely forgotten about — and I wish I could read my own account of how things were. Perspective is so important, and there's no better way to see how much you've grown and changed than reading your own (possibly melodramatic) journals.

5. Spend time with your family, especially if you have younger siblings.

One day soon you'll be off experiencing college, first jobs, roommates, solo trips, and various adventures away from home. You'll miss your family, but you'll be immersed in new things, while they may be focused on the you-shaped hole in their world. Hold them close and let them know you love them before you set off on your own path.

6. Think about what kind of college you'd like to attend — and be open to the kind of college you can happily afford.

There are so many amazing ways to go about getting a college education. Remember that many people pursue advanced degrees for years, at all stages of their careers and lives. There is no such thing as one perfect college experience, and sometimes practicality may trump an idealized vision of what's best. Be open to fantastic community colleges, colleges with big scholarship opportunities, and work opportunities that will compensate your credit hours. An education is amazing — so is a lack of debt when you get that diploma.

7. Be confident about what interests you.

Whatever makes you happy — Oxford commas, Broadway musicals, modern dance, lacrosse — pursue it. Love it, enjoy it, find other people to share the love with, and don't waste time on people who try to convince you what you love isn't cool. They're wrong. The Oxford comma is cool. Trust me, I know.

8. Enjoy your body.

Wear what you like, exercise because it feels good, dance, swim, do all those things and swagger when you do them. You're gorgeous right now, exactly the way you are, and your body is better than good enough — it's amazing, it's all yours, and you'll be in it forever. Take good care of it.

9. Take time to daydream and bask in solitude.

You're about to face new challenges and stresses. For a few years, things might only get more chaotic and complicated. Take time now to give your mind a rest, and try your best to make that mental restfulness a daily habit.

10. Friends come and go, but the lasting effects of good and bad friendships will shape you deeply.

Sometimes it's hard to acknowledge that it's time to let a friendship go, but there's peace in knowing that every friendship teaches you something important. When you do find a friend who grows with you and is there for you through thick and thin, hold on tight! Be in the moment with your friends and cherish the time you have together.

11. If you think you might like to be or do something when you're older, find out all you can about it.

Interview people in the field you want to work in. Interview people who've left the field you want to work in. Volunteer, take unpaid internships and entry level jobs, and do research in your intended field. You'll either find out it wasn't what you wanted after all, or you'll make valuable inroads and gain insider information that will make your future career incredible.

12. Read everything you can get your hands on.

Reading keeps your mind open, lets you live other lives, and shows you other peoples' perspectives. Read it all — fiction, non-fiction, light, fun novels and deep exposes, poetry and interviews. Make reading for information and pleasure a daily habit.

13. Pursue the hobbies that excite you, regardless of whether or not they pad your transcripts.

I know people who curse the hours they spent on fields and in clubs doing things they hated because they wanted their college applications to look impressive. I know people who took college courses they knew they could ace instead of courses they were interested in to keep up the perfect GPA. You have a limited amount of time to do all the things you might be passionate about. Make sure you are using that time wisely.

14. Take good care of your body, mind, and soul.

Sleeping well, eating right, exercising, meditating, spending time with loved ones — do all the things that will keep you happy and healthy so you can tackle the big challenges that are going to come your way.

15. Extend kindness.

It's so easy to extend small, kind gestures every day. Choose to be consciously kind to the people around you.

16. Take pictures.

Maybe this isn't as relevant anymore, but I mourn all the trips and vacations I took as a teenager and never bothered to photographically document. In my defense, I was young before the age of the camera phone! ;) Maybe better advice today would be "take some pictures, but don't forget to put the camera away and enjoy the moment."

17. Love yourself.

At the end of the day, you have yourself — your gorgeous, funny, smart, exciting self. Love yourself with every fiber of your body, and that love will radiate out and attract happiness into your life.

Credit: Cosmopolitan.com