My little sister is not so little anymore.

I can seriously remember the day she was born. And now, on November 14th, she is turning 15. 15 is a huge year - it's your freshman or sophomore year of high school. It's when you decide what you might possibly want to do in the future, when you decide who your friends really might be, and when you truly start to figure yourself out.

There are so many things I wish I had known at 15. In honor of my sister's birthday, here are 15 things I wish I knew at 15:

1. Smile often.

Smilling is an extremely important part of being happy. You might not be the happiest, but if you smile, it will help your day or even your life get better.

2. Don't be afraid to laugh.

Your friends might think it's lame to laugh. This is something I've seen from a ton of teenagers. If you find something funny, laugh at it. And don't be afraid to laugh at yourself.

3. Don't take others opinions into great consideration.

If someone says something that bothers you, just shake it off. As Dr. Seuss said, "Those who don't matter, don't mind."

4. Don't get stuck in the past.

If someone told you last week that they didn't like your hair, don't get stuck on that comment. Pick yourself up and keep moving.

5. If the friends you have now are not your friends later, that's okay.

One of the most devastating things to me at 15 was losing friends due to different opinions or situations.

6. Appreciate your friends and family now.

Tying into my last point, I've learned as I've gotten older to appreciate the friends I have now and cherish the memories I have with the old friends.

7. Your parent is supposed to be your parent.

Let your parents do their job and be your parent, and don't get upset with them when they do.

8. Take every opportunity.

If someone offers you the opportunity to go on a trip, take it. If they offer you a job, take it. If they offer you a volunteer opportunity, take it. All opportunities will help you improve yourself and give you different perspectives.

9. Be nice to yourself.

If you don't feel comfortable stepping out of your comfort zone just yet, that's okay. If you got an 80 on a test, that's okay. If you played a note wrong on your instrument, that's okay. If you dropped something on the floor and it got ruined, that's okay. Don't beat yourself up over little things.

10. You are smart enough.

You've probably had a bad teacher that told you that you aren't good at math. You've probably thought to yourself, "I'm not smart enough to do this." But you are.

11. You are beautiful/handsome enough.

I know some many young kids who look in the mirror and hate what they see, even though I see someting completely different.

12. If you're having issues, don't be afraid to ask for help.

If you feel way too sad and tired all the time, something might be wrong. Do not be afraid to ask for help. Go to the counselors or your parents and let them help you. It will make you feel better in the long run.

13. Don't be afraid to try new things.

If something is new and outside of your comfort zone, take a chance and do it. Then you can tell everyone you've done something you've never done before.

14. Be nice to everyone.

It doesn't matter if someone is mean to you, or if they're having a bad day, or if they have different interests than you. Be kind.

15. Be yourself.

Ultimately, being yourself is one of the most important things you can do.