Don't do anything you don't want to do
It is worth it to take the time and really think about what you want to do, regarding classes and extra-curricular activities. I spent three years in choir. I really liked my first year, but I disliked it in 10th and 11th grade. I kept going with it, because I liked it so much my first year and thought maybe I'd like it again. But I didn't! I finally got smart, didn't take it my senior year, and was much happier not wasting my time with something that I don't enjoy.
Make friends with teachers
Teachers are the best friends you can make at high schools because they are much more sane than your fellow students (in most cases). One of my closest friends I had this year was the photo teacher, and because we were friends I always had a place to go when I didn't have a class, and someone to help me with all the random things in my life. I made friends with a lot of teachers and administrators, which allowed me to get away with things other students couldn't do, haha. Also, if you are friends with a teacher, it is always easy to get good recommendations for whatever you're applying for. Of course, these weren't my reasons to befriend my teachers, I honestly just like adults way more than teenagers. But these were some good pluses!
Get involved, but not too involved
My junior year I had plans of joining FCCLA, and my senior year I had plans to join TSA. I'm also a full time student, part time employee, and a piano teacher with a blog, family, and friends. It turns out, you can't do everything, and it is not worth overwhelming yourself to join every club and take every challenging class even if you truly want to. Of course, there are those kids out there that don't get as stressed as I do, and can do pretty much everything. But most of us are not like that, and that is okay! Just pick what is most important to you, and be happy with that.
Be smart about getting college credit, but don't overdo it
Throughout all of my high school years, I felt obligated to get as much college credit as I could. My mom, though, would always remind me that it is okay to not complete your associate's in high school, and that I should focus more on enjoying high school and doing things that I like. I'm really grateful she told me that so often, and that I listened, because I had tons of fun in high school! I did take lots of classes to get college credit, but I was careful not to do anything that would stress me out too much. I'm glad I had the challenge of AP Calculus, but I'm even more glad that I found an easier way to get college credit than AP classes. Distance education was definitely more my thing, because I was promised the credit rather than the gamble of a big test. College generals are much easier than AP classes make them out to be, so if you aren't up for taking AP classes, don't sweat it. You have to go to college anyway.
Motivate yourself so others don't have to
Being a teenager, I hate it so much when people tell me what to do. So I try to do things before people tell me to do them. It is so frustrating to me to see kids who are being pushed and nagged to do what they are supposed to do, then they end up doing them anyway. Wouldn't it have saved so much time if they just did what they were supposed to in the first place? That's what you've got to understand. You've got to do your homework, study, and go to class. So just get it over with and do it. It will save time in the long run.
If someone won't match with you, they aren't your true friend
I've really never understood why people are embarrassed to be matching.
People grow apart, and that's okay
This was a strange one for me to learn. I've had lots of friends over the past couple of years, but usually they are kind of the same from year to year, and a lot of them I've known since jr high and even elementary school. It's kind of sad, but people grow and change throughout high school, and I guess it is normal to slowly get more and more different than a formerly close friend and then suddenly realize you aren't as tight as you once were. Then it is kind of awkward because you are still friends out of obligation, and you don't really know how often you're supposed to text and hang out when really you have other people you want to spend time with. Sometimes it is healthier just to let go.
Time goes fast
How cliche! This is the one everyone knows, but I learned it thoroughly for myself, so I thought I'd add it. It seems like yesterday was my first day of cross country practice as an eager little freshman who had tons of schooling ahead of her. Sometimes it seemed long throughout these years, and I had some major senioritis during my junior year. But, it all went by quicker than I can describe! High school, and all of your schooling in general, is but a small portion of your life. So don't get caught up in wishing you were done and could move on with your life. Because guess what? Once school is over, you just get to work. For the rest of your life.
So there's just a few things I've learned over the course of my years! It is strange leaving now, but I'm pretty excited to start this new chapter of my life. I'm also excited to see who gets engaged and called on missions in these next few months, haha.