As a senior in high school, I often think about where my life has gone. I remember, when I was little, going to birthday parties and sleepovers, and living life without any care in the world.
Then came high school.... High School, while it is a place to enjoy your time with your close friends, is an important time to develop yourself as an individual. It is a time to define your passions, your like, your dislikes. As I've already reached pretty much the end of high school, I am talking about this from experience.
While in high school, you'll become a senior in a blink of an eye, and at that point, you need to start applying for college or doing whatever you wish to endeavor, and in order to do this, you need to define yourself as an unique individual. While this may sound hard, it is not hard, as long as you start as early as possible. The easiest way to develop yourself is to do extracurricular activities like band, track, swimming, tennis, or whatever you like to do. By doing this, you can develop a good circle of friends really quickly, while advancing your passions.
In the end, while you need to do a lot while in high school, make sure you enjoy your high school years, because once you leave, you'll have a lot on your hands before you can re-live those moments.